Tapas Goswami

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• Website

Education / Work History

• Assistant Professor, UPES India (2017–present)
• Ph.D. Scholar, IIT Kanpur (2010)
• M.Sc., University of Burdwan, West Bengal, India
• B.Sc., University of Burdwan, West Bengal, India

Thesis Abstract

Controlling laser induced photochemistry in supersonic molecular beam and probing ultrafast dynamics in liquid phase

My thesis deals with ultrafast studies in two important phases of matter: gas and liquid. The main aim of this thesis is to control some femtosecond laser induced photochemistry in supersonic molecular beam. An additional aim is to probe the ultrafast dynamics in more complicated system in the liquid phase using femtosecond degenerate pump-probe and photon echo spectroscopy technique. The thesis has been organized into seven chapters. The thesis starts with a brief discussion on the motivation behind the present work (Chapter 1). This introductory chapter also includes a brief introduction to coherent control and a short history of the molecular beam technique. In Chapter 2, the instrumentation part for the construction of supersonic molecular beam chamber with linear time of flight mass spectrometer is discussed in detail. In Chapter 3, different femtosecond laser systems used in the experiments, are described thoroughly. Different types of pulse characterization techniques are presented. Design and construction of a high power, white light seeded double pass non-collinear optical parametric amplifier (NOPA) in the visible wavelength using a simple amplifier crystal is also included. In Chapter 4, control of laser induced molecular fragmentation of n-propyl benzene using different control parameter of the laser pulses is described. In this chapter, first, the effect of chirping a femtosecond laser pulse on the fragmentation of n-propyl benzene is presented. Simultaneous effect of chirp and polarization as two control parameters for the non-resonant photodissociation of n-propyl benzene is also explored. In Chapter 5, using femtosecond time resolved degenerate pump-probe mass spectrometry; we elucidate that the dynamics of retro-Diels-Alder reaction of dicyclopentadiene (DCPD) to cyclopentadiene (CPD) in supersonic molecular beam occurs on ultrafast timescales. This femtosecond laser driven retro-Diels-Alder reaction is then controlled by using linearly chirped frequency modulated pulses. In Chapter 6, dependence of ultrafast dynamics for the excited state evolution and ground state recovery of a cyanine dye (IR125) in dichloromethane (DCM) solvent interfaced with neat water is presented. Excited state dynamics of some metal-octaethyl porphyrins (OEP) like Zn(II)-OEP, Ni(II)-OEP, Co(II)-OEP is studied by time evolving photon echo spectra for different values of coherence and population relaxation times. The concluding chapter, Chapter 7, summarizes all the work presented in the thesis. A future direction to the current work is proposed.

Research Topic / Interest

Contact me to know my current interests.

Publications

These include only those published in our lab.

1. Synthesis, Structure, and Two-Photon Absorption Studies of a Phosphorus-Based Tris Hydrazone Ligand (S)P[N(Me)N═CH-C6H3-2-OH-4-N(CH2CH3)2]3 and Its Metal Complexes. V. Chandrasekhar, R. Azhakar, B. Murugesapandian, T. Senapati, P. Bag, M. D. Pandey, S. K. Maurya, and D. Goswami, Inorganic Chemistry 49(9), 4008–4016 (2010) [Abstract] [PDF] [BibTeX]

   Abstract: A phosphorus-supported multidentate ligand (S)P[N(Me)N═CH-C6H3-2-OH-4-N(CH 2CH3)2]3 (1) has been used to prepare mononuclear complexes LM [M = Fe (2) Co (3)] and trinuclear complexes L2M3 [M = Mn (4), Ni (5), Zn (6), Mg (7), Cd (8)]. In both 2 and 3 the ligand binds the metal ion in a facial coordination mode utilizing three imino nitrogen (3N) and three phenolic oxygen (3O) atoms. The molecular structures of L2Mn3, L2Ni3, L2Zn3, L2Mg3, and L2Cd3 (4−8) are similar; two trihydrazone ligands are involved in coordination to hold the three metal ions in a linear fashion. Each of the trishydrazone ligands behaves as a trianionic hexadentate ligand providing three imino and three phenolic oxygen atoms for coordination to the metal ions. The coordination environment around the two terminal metal ions is similar (3N, 3O) while the central metal ion has a 6O coordination environment. Third-order non-linear optical properties of these compounds as measured by their two-photon absorption (TPA) cross section reveals that while 1 does not possess obvious TPA activity, complexes 2 (3213 GM) and 4 (3516 GM) possess a large TPA cross section at 770 nm.

    BibTeX: @article{chandrasekharSynthesisStructureTwoPhoton2010,
     title = {Synthesis, {{Structure}}, and {{Two-Photon Absorption Studies}} of a {{Phosphorus-Based Tris Hydrazone Ligand}} ({{S}}){{P}}[{{N}}({{Me}}){{N}}═{{CH-C6H3-2-OH-4-N}}({{CH2CH3}})2]3 and {{Its Metal Complexes}}},
     author = {Chandrasekhar, Vadapalli and Azhakar, Ramachandran and Murugesapandian, Balasubramanian and Senapati, Tapas and Bag, Prasenjit and Pandey, Mrituanjay D. and Maurya, Sandeep Kumar and Goswami, Debabrata},
     date = {2010-05-03},
     journaltitle = {Inorganic Chemistry},
     shortjournal = {Inorg. Chem.},
     volume = {49},
     number = {9},
     pages = {4008--4016},
     issn = {0020-1669},
     doi = {10/bvqgfp},
     url = {https://doi.org/10.1021/ic901531e},
     urldate = {2019-08-14}
   }
   

2. Control of Femtosecond Laser Driven Retro-Diels-Alder-like Reaction of Dicyclopentadiene. D. K. Das, T. Goswami, and D. Goswami, in Photonics 2010: Tenth International Conference on Fiber Optics and Photonics (International Society for Optics and Photonics, 2011), 8173, p. 81730O [Abstract] [PDF] [BibTeX]

   Abstract: Using femtosecond time resolved degenerate pump-probe mass spectrometry coupled with simple linearly chirped frequency modulated pulse, we elucidate that the dynamics of retro-Diels-Alder reaction of diclopentadiene (DCPD) to cyclopentadiene (CPD) in supersonic molecular beam occurs in ultrafast time scale. Negatively chirped pulse enhances the ion yield of CPD, as compared to positively chirped pulse. This indicates that by changing the frequency (chirp) of the laser pulse we can control the ion yield of a chemical reaction.

    BibTeX: @inproceedings{dasControlFemtosecondLaser2011,
     title = {Control of Femtosecond Laser Driven Retro-{{Diels-Alder-like}} Reaction of Dicyclopentadiene},
     booktitle = {Photonics 2010: {{Tenth International Conference}} on {{Fiber Optics}} and {{Photonics}}},
     author = {Das, Dipak Kumar and Goswami, Tapas and Goswami, Debabrata},
     date = {2011-08-23},
     volume = {8173},
     pages = {81730O},
     publisher = {{International Society for Optics and Photonics}},
     doi = {10/dsc8s7},
     url = {https://www.spiedigitallibrary.org/conference-proceedings-of-spie/8173/81730O/Control-of-femtosecond-laser-driven-retro-Diels-Alder-like-reaction/10.1117/12.897909.short},
     urldate = {2019-08-13},
     eventtitle = {Photonics 2010: {{Tenth International Conference}} on {{Fiber Optics}} and {{Photonics}}}
   }
   

3. Control of Laser Induced Molecular Fragmentation of N-Propyl Benzene Using Chirped Femtosecond Laser Pulses. T. Goswami, S. K. Karthick Kumar, A. Dutta, and D. Goswami, Chemical Physics 360(1), 47–52 (2009) [Abstract] [PDF] [BibTeX]

   Abstract: We present the effect of chirping a femtosecond laser pulse on the fragmentation of n-propyl benzene. An enhancement of an order of magnitude for the relative yields of C3H3+ and C5H5+ in the case of negatively chirped pulses and C6H5+ in the case of positively chirped pulses with respect to the transform-limited pulse indicates that in some fragmentation channel, coherence of the laser field plays an important role. For the relative yield of all other heavier fragment ions, resulting from the interaction of the intense laser field with the molecule, there is no such enhancement effect with the sign of chirp, within experimental errors. The importance of the laser phase is further reinforced through a direct comparison of the fragmentation results with the second harmonic of the chirped laser pulse with identical bandwidth.

    BibTeX: @article{goswamiControlLaserInduced2009,
     title = {Control of Laser Induced Molecular Fragmentation of N-Propyl Benzene Using Chirped Femtosecond Laser Pulses},
     author = {Goswami, Tapas and Karthick Kumar, S. K. and Dutta, Aveek and Goswami, Debabrata},
     date = {2009-06-12},
     journaltitle = {Chemical Physics},
     shortjournal = {Chemical Physics},
     volume = {360},
     number = {1},
     pages = {47--52},
     issn = {0301-0104},
     doi = {10/b2h79c},
     url = {http://www.sciencedirect.com/science/article/pii/S0301010409001219},
     urldate = {2019-08-14}
   }
   

4. Controlling the Femtosecond Laser-Driven Transformation of Dicyclopentadiene into Cyclopentadiene. T. Goswami, D. K. Das, and D. Goswami, Chemical Physics Letters 558, 1–7 (2013) [Abstract] [PDF] [BibTeX]

   Abstract: Dynamics of the chemical transformation of dicyclopentadiene into cyclopentadiene in a supersonic molecular beam is elucidated using femtosecond time-resolved degenerate pump–probe mass spectrometry. Control of this ultrafast chemical reaction is achieved by using linearly chirped frequency modulated pulses. We show that negatively chirped femtosecond laser pulses enhance the cyclopentadiene photoproduct yield by an order of magnitude as compared to that of the unmodulated or the positively chirped pulses. This demonstrates that the phase structure of femtosecond laser pulse plays an important role in determining the outcome of a chemical reaction.

    BibTeX: @article{goswamiControllingFemtosecondLaserdriven2013,
     title = {Controlling the Femtosecond Laser-Driven Transformation of Dicyclopentadiene into Cyclopentadiene},
     author = {Goswami, Tapas and Das, Dipak K. and Goswami, Debabrata},
     date = {2013-02-12},
     journaltitle = {Chemical Physics Letters},
     shortjournal = {Chemical Physics Letters},
     volume = {558},
     pages = {1--7},
     issn = {0009-2614},
     doi = {10/f4nnb2},
     url = {https://my.pcloud.com/publink/show?code=XZFvxr7ZpduyXffXsJj4NXDLmSt1zLjBhELV},
     urldate = {2019-08-02}
   }
   

5. Hot Chemistry with Cold Molecules. T. Goswami and D. Goswami, in Laser Pulse Phenomena and Applications (BoD – Books on Demand, 2010), pp. 371–388 [Abstract] [BibTeX]

   Abstract: Pulsed lasers are available in the gas, liquid, and the solid state. These lasers are also enormously versatile in their output characteristics yielding emission from very large energy pulses to very high peak-power pulses. Pulsed lasers are equally versatile in their spectral characteristics. This volume includes an impressive array of current research on pulsed laser phenomena and applications. Laser Pulse Phenomena and Applications covers a wide range of topics from laser powered orbital launchers, and laser rocket engines, to laser-matter interactions, detector and sensor laser technology, laser ablation, and biological applications.

    BibTeX: @incollection{goswamiHotChemistryCold2010,
     title = {Hot {{Chemistry}} with {{Cold Molecules}}},
     booktitle = {Laser {{Pulse Phenomena}} and {{Applications}}},
     author = {Goswami, Tapas and Goswami, Debabrata},
     date = {2010-12-30},
     eprint = {5XSfDwAAQBAJ},
     eprinttype = {googlebooks},
     pages = {371--388},
     publisher = {{BoD – Books on Demand}},
     isbn = {978-953-307-405-4}
   }
   

6. Probing the Ultrafast Solution Dynamics of a Cyanine Dye in an Organic Solvent Interfaced with Water. T. Goswami, S. K. K. Kumar, A. Dutta, and D. Goswami, The Journal of Physical Chemistry B 113(51), 16332–16336 (2009) [Abstract] [PDF] [BibTeX]

   Abstract: Dependence of ultrafast dynamics on the excited state evolution and ground state recovery of a cyanine dye (IR125) in dichloromethane (DCM) solvent interfaced with neat water is presented. We use degenerate pump−probe transient absorption spectroscopy to show that the excited-state dynamics of the dye molecule is strongly dependent on the position of the measurements from bulk DCM solution to the solution near the water layer. The decay component of the transient corresponding to the excited state lifetime increases from bulk DCM solution to its interface with water. Such results show that the effect of the presence of water layer over the dye solution in DCM extends several micrometers, indicating the surfactant nature of the IR125 molecules, and provides us a measure of the penetration of water into the DCM layer. The initial ultrafast decay component (coherent spike) directly correlates to the pulse-width of our near-transform limited pulses used in these experiments. This approach of measuring the excited state decay of a dye across an immiscible liquid interface can provide important characteristics of microtransport across such interfaces.

    BibTeX: @article{goswamiProbingUltrafastSolution2009,
     title = {Probing the {{Ultrafast Solution Dynamics}} of a {{Cyanine Dye}} in an {{Organic Solvent Interfaced}} with {{Water}}},
     author = {Goswami, Tapas and Kumar, S. K. Karthick and Dutta, Aveek and Goswami, Debabrata},
     date = {2009-12-24},
     journaltitle = {The Journal of Physical Chemistry B},
     shortjournal = {J. Phys. Chem. B},
     volume = {113},
     number = {51},
     pages = {16332--16336},
     issn = {1520-6106},
     doi = {10/dc3b67},
     url = {https://doi.org/10.1021/jp903753u},
     urldate = {2019-08-14}
   }
   

7. Towards Using Molecular Ions as Qubits: Femtosecond Control of Molecular Fragmentation with Multiple Knobs. T. Goswami, D. K. Das, and D. Goswami, Pramana 75(6), 1065–1069 (2010) [Abstract] [PDF] [BibTeX]

   Abstract: Non-resonant molecular fragmentation of n-propyl benzene with femtosecond laser pulses is dependent on the phase and polarization characteristics of the laser. We find that the effect of the chirp and polarization of the femtosecond pulse when applied simultaneously is mutually independent of each other, which makes chirp and polarization as useful ‘logic’ implementing knobs.

    BibTeX: @article{goswamiUsingMolecularIons2010,
     title = {Towards Using Molecular Ions as Qubits: {{Femtosecond}} Control of Molecular Fragmentation with Multiple Knobs},
     shorttitle = {Towards Using Molecular Ions as Qubits},
     author = {Goswami, Tapas and Das, Dipak K. and Goswami, Debabrata},
     date = {2010-12-01},
     journaltitle = {Pramana},
     shortjournal = {Pramana - J Phys},
     volume = {75},
     number = {6},
     pages = {1065--1069},
     issn = {0973-7111},
     doi = {10/cf945s},
     url = {https://doi.org/10.1007/s12043-010-0190-9},
     urldate = {2019-08-14}
   }
   

8. Towards Using Molecular States as Qubits. D. Goswami, T. Goswami, S. K. K. Kumar, and D. K. Das, AIP Conference Proceedings 1384(1), 251–253 (2011) [Abstract] [PDF] [BibTeX]

   Abstract: Molecular systems are presented as possible qubit systems by exploring non‐resonant molecular fragmentation of n‐propyl benzene with femtosecond laser pulses as a model case. We show that such laser fragmentation process is dependent on the phase and polarization characteristics of the laser. The effect of the chirp and polarization of the femtosecond pulse when applied simultaneously is mutually independent of each other, which makes chirp and polarization as useful ‘logic’ implementing parameters for such molecular qubits.

    BibTeX: @article{goswamiUsingMolecularStates2011,
     title = {Towards {{Using Molecular States}} as {{Qubits}}},
     author = {Goswami, Debabrata and Goswami, Tapas and Kumar, S. K. Karthick and Das, Dipak K.},
     date = {2011-09-23},
     journaltitle = {AIP Conference Proceedings},
     shortjournal = {AIP Conference Proceedings},
     volume = {1384},
     number = {1},
     pages = {251--253},
     issn = {0094-243X},
     doi = {10/bfnp4m},
     url = {https://aip.scitation.org/doi/abs/10.1063/1.3635869},
     urldate = {2019-08-02}
   }
   

9. Structure and Hydrogen Bond Vibrations of the Jet-Cooled 1:1 Complex between 7-Azaindole and Formamide: A Laser-Induced Fluorescence Spectroscopy Study. M. K. Hazra, M. Mukherjee, D. Goswami, and T. Chakraborty, Chemical Physics Letters 503(4), 203–209 (2011) [Abstract] [PDF] [BibTeX]

   Abstract: Laser-induced fluorescence spectra of 7-azaindole⋯formamide complex are measured in a supersonic free jet expansion. Calculation at MP2/6-311++G∗∗ level predicts a cyclic doubly hydrogen-bonded structure for the complex is favoured most in the ground state. The complex emits only UV fluorescence from the locally excited state and tautomerization is inhibited under the jet-cooled environment. This photophysical behavior is consistent with the predictions of CIS/6-311++G∗∗ and TDDFT/6-311++G∗∗ calculations. The low-frequency bands in the fluorescence spectra are assigned to different hydrogen bond modes of the complex, and the spectra reveal signatures of mixing between inter- and intra-molecular vibrational modes in the excited state.

    BibTeX: @article{hazraStructureHydrogenBond2011,
     title = {Structure and Hydrogen Bond Vibrations of the Jet-Cooled 1:1 Complex between 7-Azaindole and Formamide: {{A}} Laser-Induced Fluorescence Spectroscopy Study},
     shorttitle = {Structure and Hydrogen Bond Vibrations of the Jet-Cooled 1},
     author = {Hazra, Montu K. and Mukherjee, Moitrayee and Goswami, Debabrata and Chakraborty, Tapas},
     date = {2011-02-17},
     journaltitle = {Chemical Physics Letters},
     shortjournal = {Chemical Physics Letters},
     volume = {503},
     number = {4},
     pages = {203--209},
     issn = {0009-2614},
     doi = {10/bj9kdz},
     url = {http://www.sciencedirect.com/science/article/pii/S000926141100025X},
     urldate = {2019-08-13}
   }
   

10. Spectrally Resolved Photon Echo Spectroscopy of Zn(II), Co(II) and Ni(II)–Octaethyl Porphyrins. S. K. Karthick Kumar, V. Tiwari, T. Goswami, and D. Goswami, Chemical Physics Letters 476(1), 31–36 (2009) [Abstract] [PDF] [BibTeX]

    Abstract: Spectrally resolved femtosecond three-pulse photon echo signal from some metal–octaethyl porphyrins (OEPs) like Zn(II)–OEP, Ni(II)–OEP, Co(II)–OEP is reported. Excited state dynamics is studied by time evolving photon echo spectra for different values of coherence and population relaxation times. Dependence on the spectrally resolved photon echo spectra on varying metal center is analyzed. For all these metallo-porphyrins, the electronic relaxation timescale is found to be limited by our laser pulsewidth of 50fs whereas the timescale for intramolecular vibrational relaxation, occurring within the Q00 band was found to be over a picosecond for Co(II)–OEP and Ni(II)–OEP and within a picosecond for Zn(II)–OEP.

     BibTeX: @article{karthickkumarSpectrallyResolvedPhoton2009,
      title = {Spectrally Resolved Photon Echo Spectroscopy of {{Zn}}({{II}}), {{Co}}({{II}}) and {{Ni}}({{II}})–Octaethyl Porphyrins},
      author = {Karthick Kumar, S. K. and Tiwari, Vivek and Goswami, Tapas and Goswami, Debabrata},
      date = {2009-07-07},
      journaltitle = {Chemical Physics Letters},
      shortjournal = {Chemical Physics Letters},
      volume = {476},
      number = {1},
      pages = {31--36},
      issn = {0009-2614},
      doi = {10/fpmh7d},
      url = {http://www.sciencedirect.com/science/article/pii/S0009261409006666},
      urldate = {2019-08-14}
    }
    

11. Probing the Ultrafast Solution Dynamics of a Cyanine Dye in an Organic Solvent Interfaced with Water. T. Goswami, S. K. K. Kumar, A. Dutta, and D. Goswami, J. Phys. Chem. B 113(51), 16332–16336 (2009) [Abstract] [PDF] [BibTeX]

    Abstract: Dependence of ultrafast dynamics on the excited state evolution and ground state recovery of a cyanine dye (IR125) in dichloromethane (DCM) solvent interfaced with neat water is presented. We use degenerate pump−probe transient absorption spectroscopy to show that the excited-state dynamics of the dye molecule is strongly dependent on the position of the measurements from bulk DCM solution to the solution near the water layer. The decay component of the transient corresponding to the excited state lifetime increases from bulk DCM solution to its interface with water. Such results show that the effect of the presence of water layer over the dye solution in DCM extends several micrometers, indicating the surfactant nature of the IR125 molecules, and provides us a measure of the penetration of water into the DCM layer. The initial ultrafast decay component (coherent spike) directly correlates to the pulse-width of our near-transform limited pulses used in these experiments. This approach of measuring the excited state decay of a dye across an immiscible liquid interface can provide important characteristics of microtransport across such interfaces.

     BibTeX: @article{goswamiProbingUltrafastSolution2010,
      title = {Probing the {{Ultrafast Solution Dynamics}} of a {{Cyanine Dye}} in an {{Organic Solvent Interfaced}} with {{Water}}},
      volume = {113},
      issn = {1520-6106},
      url = {https://doi.org/10.1021/jp903753u},
      doi = {10/dc3b67},
      number = {51},
      journaltitle = {J. Phys. Chem. B},
      urldate = {2019-08-14},
      date = {2009-12-24},
      pages = {16332-16336},
      author = {Goswami, Tapas and Kumar, S. K. Karthick and Dutta, Aveek and Goswami, Debabrata}
    }
    

12. Spectrally Resolved Photon Echo Spectroscopy of Zn(II), Co(II) and Ni(II)–Octaethyl Porphyrins. S. K. Karthick Kumar, V. Tiwari, T. Goswami, and D. Goswami, Chemical Physics Letters 476(1), 31–36 (2009) [Abstract] [PDF] [BibTeX]

    Abstract: Spectrally resolved femtosecond three-pulse photon echo signal from some metal–octaethyl porphyrins (OEPs) like Zn(II)–OEP, Ni(II)–OEP, Co(II)–OEP is reported. Excited state dynamics is studied by time evolving photon echo spectra for different values of coherence and population relaxation times. Dependence on the spectrally resolved photon echo spectra on varying metal center is analyzed. For all these metallo-porphyrins, the electronic relaxation timescale is found to be limited by our laser pulsewidth of 50fs whereas the timescale for intramolecular vibrational relaxation, occurring within the Q00 band was found to be over a picosecond for Co(II)–OEP and Ni(II)–OEP and within a picosecond for Zn(II)–OEP.

     BibTeX: @article{karthickkumarSpectrallyResolvedPhoton2010,
      title = {Spectrally Resolved Photon Echo Spectroscopy of {{Zn}}({{II}}), {{Co}}({{II}}) and {{Ni}}({{II}})–Octaethyl Porphyrins},
      volume = {476},
      issn = {0009-2614},
      url = {http://www.sciencedirect.com/science/article/pii/S0009261409006666},
      doi = {10/fpmh7d},
      number = {1},
      journaltitle = {Chemical Physics Letters},
      urldate = {2019-08-14},
      date = {2009-07-07},
      pages = {31-36},
      author = {Karthick Kumar, S. K. and Tiwari, Vivek and Goswami, Tapas and Goswami, Debabrata}
    }
    

13. Control of Laser Induced Molecular Fragmentation of N-Propyl Benzene Using Chirped Femtosecond Laser Pulses. T. Goswami, S. K. Karthick Kumar, A. Dutta, and D. Goswami, Chemical Physics 360(1), 47–52 (2009) [Abstract] [PDF] [BibTeX]

    Abstract: We present the effect of chirping a femtosecond laser pulse on the fragmentation of n-propyl benzene. An enhancement of an order of magnitude for the relative yields of C3H3+ and C5H5+ in the case of negatively chirped pulses and C6H5+ in the case of positively chirped pulses with respect to the transform-limited pulse indicates that in some fragmentation channel, coherence of the laser field plays an important role. For the relative yield of all other heavier fragment ions, resulting from the interaction of the intense laser field with the molecule, there is no such enhancement effect with the sign of chirp, within experimental errors. The importance of the laser phase is further reinforced through a direct comparison of the fragmentation results with the second harmonic of the chirped laser pulse with identical bandwidth.

     BibTeX: @article{goswamiControlLaserInduced2010,
      title = {Control of Laser Induced Molecular Fragmentation of N-Propyl Benzene Using Chirped Femtosecond Laser Pulses},
      volume = {360},
      issn = {0301-0104},
      url = {http://www.sciencedirect.com/science/article/pii/S0301010409001219},
      doi = {10/b2h79c},
      number = {1},
      journaltitle = {Chemical Physics},
      urldate = {2019-08-14},
      date = {2009-06-12},
      pages = {47-52},
      author = {Goswami, Tapas and Karthick Kumar, S. K. and Dutta, Aveek and Goswami, Debabrata}
    }
    

14. Controlling the Femtosecond Laser-Driven Transformation of Dicyclopentadiene into Cyclopentadiene. T. Goswami, D. K. Das, and D. Goswami, Chemical Physics Letters 558, 1–7 (2013) [Abstract] [PDF] [BibTeX]

    Abstract: Dynamics of the chemical transformation of dicyclopentadiene into cyclopentadiene in a supersonic molecular beam is elucidated using femtosecond time-resolved degenerate pump–probe mass spectrometry. Control of this ultrafast chemical reaction is achieved by using linearly chirped frequency modulated pulses. We show that negatively chirped femtosecond laser pulses enhance the cyclopentadiene photoproduct yield by an order of magnitude as compared to that of the unmodulated or the positively chirped pulses. This demonstrates that the phase structure of femtosecond laser pulse plays an important role in determining the outcome of a chemical reaction.

     BibTeX: @article{goswamiControllingFemtosecondLaserdriven2014,
      title = {Controlling the Femtosecond Laser-Driven Transformation of Dicyclopentadiene into Cyclopentadiene},
      volume = {558},
      issn = {0009-2614},
      url = {https://my.pcloud.com/publink/show?code=XZFvxr7ZpduyXffXsJj4NXDLmSt1zLjBhELV},
      doi = {10/f4nnb2},
      journaltitle = {Chemical Physics Letters},
      urldate = {2019-08-02},
      date = {2013-02-12},
      pages = {1-7},
      author = {Goswami, Tapas and Das, Dipak K. and Goswami, Debabrata}
    }
    

15. Towards Using Molecular States as Qubits. D. Goswami, T. Goswami, S. K. K. Kumar, and D. K. Das, AIP Conference Proceedings 1384(1), 251–253 (2011) [Abstract] [PDF] [BibTeX]

    Abstract: Molecular systems are presented as possible qubit systems by exploring non‐resonant molecular fragmentation of n‐propyl benzene with femtosecond laser pulses as a model case. We show that such laser fragmentation process is dependent on the phase and polarization characteristics of the laser. The effect of the chirp and polarization of the femtosecond pulse when applied simultaneously is mutually independent of each other, which makes chirp and polarization as useful ‘logic’ implementing parameters for such molecular qubits.

     BibTeX: @article{goswamiUsingMolecularStates2012,
      title = {Towards {{Using Molecular States}} as {{Qubits}}},
      volume = {1384},
      issn = {0094-243X},
      url = {https://aip.scitation.org/doi/abs/10.1063/1.3635869},
      doi = {10/bfnp4m},
      number = {1},
      journaltitle = {AIP Conference Proceedings},
      urldate = {2019-08-02},
      date = {2011-09-23},
      pages = {251-253},
      author = {Goswami, Debabrata and Goswami, Tapas and Kumar, S. K. Karthick and Das, Dipak K.}
    }
    

16. Control of Femtosecond Laser Driven Retro-Diels-Alder-like Reaction of Dicyclopentadiene. D. K. Das, T. Goswami, and D. Goswami, in Photonics 2010: Tenth International Conference on Fiber Optics and Photonics (International Society for Optics and Photonics, 2011), 8173, p. 81730O [Abstract] [PDF] [BibTeX]

    Abstract: Using femtosecond time resolved degenerate pump-probe mass spectrometry coupled with simple linearly chirped frequency modulated pulse, we elucidate that the dynamics of retro-Diels-Alder reaction of diclopentadiene (DCPD) to cyclopentadiene (CPD) in supersonic molecular beam occurs in ultrafast time scale. Negatively chirped pulse enhances the ion yield of CPD, as compared to positively chirped pulse. This indicates that by changing the frequency (chirp) of the laser pulse we can control the ion yield of a chemical reaction.

     BibTeX: @inproceedings{dasControlFemtosecondLaser2012,
      title = {Control of Femtosecond Laser Driven Retro-{{Diels}}-{{Alder}}-like Reaction of Dicyclopentadiene},
      volume = {8173},
      url = {https://www.spiedigitallibrary.org/conference-proceedings-of-spie/8173/81730O/Control-of-femtosecond-laser-driven-retro-Diels-Alder-like-reaction/10.1117/12.897909.short},
      doi = {10/dsc8s7},
      eventtitle = {Photonics 2010: {{Tenth International Conference}} on {{Fiber Optics}} and {{Photonics}}},
      booktitle = {Photonics 2010: {{Tenth International Conference}} on {{Fiber Optics}} and {{Photonics}}},
      publisher = {{International Society for Optics and Photonics}},
      urldate = {2019-08-13},
      date = {2011-08-23},
      pages = {81730O},
      author = {Das, Dipak Kumar and Goswami, Tapas and Goswami, Debabrata}
    }
    

17. Structure and Hydrogen Bond Vibrations of the Jet-Cooled 1:1 Complex between 7-Azaindole and Formamide: A Laser-Induced Fluorescence Spectroscopy Study. M. K. Hazra, M. Mukherjee, D. Goswami, and T. Chakraborty, Chemical Physics Letters 503(4), 203–209 (2011) [Abstract] [PDF] [BibTeX]

    Abstract: Laser-induced fluorescence spectra of 7-azaindole⋯formamide complex are measured in a supersonic free jet expansion. Calculation at MP2/6-311++G∗∗ level predicts a cyclic doubly hydrogen-bonded structure for the complex is favoured most in the ground state. The complex emits only UV fluorescence from the locally excited state and tautomerization is inhibited under the jet-cooled environment. This photophysical behavior is consistent with the predictions of CIS/6-311++G∗∗ and TDDFT/6-311++G∗∗ calculations. The low-frequency bands in the fluorescence spectra are assigned to different hydrogen bond modes of the complex, and the spectra reveal signatures of mixing between inter- and intra-molecular vibrational modes in the excited state.

     BibTeX: @article{hazraStructureHydrogenBond2012,
      title = {Structure and Hydrogen Bond Vibrations of the Jet-Cooled 1:1 Complex between 7-Azaindole and Formamide: {{A}} Laser-Induced Fluorescence Spectroscopy Study},
      volume = {503},
      issn = {0009-2614},
      url = {http://www.sciencedirect.com/science/article/pii/S000926141100025X},
      doi = {10.1016/j.cplett.2011.01.019},
      shorttitle = {Structure and Hydrogen Bond Vibrations of the Jet-Cooled 1},
      number = {4},
      journaltitle = {Chemical Physics Letters},
      urldate = {2019-08-13},
      date = {2011-02-17},
      pages = {203-209},
      author = {Hazra, Montu K. and Mukherjee, Moitrayee and Goswami, Debabrata and Chakraborty, Tapas}
    }
    

18. Hot Chemistry with Cold Molecules. T. Goswami and D. Goswami, in Laser Pulse Phenomena and Applications (BoD – Books on Demand, 2010), pp. 371–388 [Abstract] [BibTeX]

    Abstract: Pulsed lasers are available in the gas, liquid, and the solid state. These lasers are also enormously versatile in their output characteristics yielding emission from very large energy pulses to very high peak-power pulses. Pulsed lasers are equally versatile in their spectral characteristics. This volume includes an impressive array of current research on pulsed laser phenomena and applications. Laser Pulse Phenomena and Applications covers a wide range of topics from laser powered orbital launchers, and laser rocket engines, to laser-matter interactions, detector and sensor laser technology, laser ablation, and biological applications.

     BibTeX: @incollection{goswamiHotChemistryCold2011,
      langid = {english},
      title = {Hot {{Chemistry}} with {{Cold Molecules}}},
      isbn = {978-953-307-405-4},
      booktitle = {Laser {{Pulse Phenomena}} and {{Applications}}},
      publisher = {{BoD – Books on Demand}},
      date = {2010-12-30},
      pages = {371-388},
      author = {Goswami, Tapas and Goswami, Debabrata},
      eprinttype = {googlebooks}
    }
    

19. Towards Using Molecular Ions as Qubits: Femtosecond Control of Molecular Fragmentation with Multiple Knobs. T. Goswami, D. K. Das, and D. Goswami, Pramana - J Phys 75(6), 1065–1069 (2010) [Abstract] [PDF] [BibTeX]

    Abstract: Non-resonant molecular fragmentation of n-propyl benzene with femtosecond laser pulses is dependent on the phase and polarization characteristics of the laser. We find that the effect of the chirp and polarization of the femtosecond pulse when applied simultaneously is mutually independent of each other, which makes chirp and polarization as useful ‘logic’ implementing knobs.

     BibTeX: @article{goswamiUsingMolecularIons2011,
      langid = {english},
      title = {Towards Using Molecular Ions as Qubits: {{Femtosecond}} Control of Molecular Fragmentation with Multiple Knobs},
      volume = {75},
      issn = {0973-7111},
      url = {https://doi.org/10.1007/s12043-010-0190-9},
      doi = {10.1007/s12043-010-0190-9},
      shorttitle = {Towards Using Molecular Ions as Qubits},
      number = {6},
      journaltitle = {Pramana - J Phys},
      urldate = {2019-08-14},
      date = {2010-12-01},
      pages = {1065-1069},
      author = {Goswami, Tapas and Das, Dipak K. and Goswami, Debabrata}
    }
    

20. Synthesis, Structure, and Two-Photon Absorption Studies of a Phosphorus-Based Tris Hydrazone Ligand (S)P[N(Me)N═CH-C6H3-2-OH-4-N(CH2CH3)2]3 and Its Metal Complexes. V. Chandrasekhar, R. Azhakar, B. Murugesapandian, T. Senapati, P. Bag, M. D. Pandey, S. K. Maurya, and D. Goswami, Inorg. Chem. 49(9), 4008–4016 (2010) [Abstract] [PDF] [BibTeX]

    Abstract: A phosphorus-supported multidentate ligand (S)P[N(Me)N═CH-C6H3-2-OH-4-N(CH 2CH3)2]3 (1) has been used to prepare mononuclear complexes LM [M = Fe (2) Co (3)] and trinuclear complexes L2M3 [M = Mn (4), Ni (5), Zn (6), Mg (7), Cd (8)]. In both 2 and 3 the ligand binds the metal ion in a facial coordination mode utilizing three imino nitrogen (3N) and three phenolic oxygen (3O) atoms. The molecular structures of L2Mn3, L2Ni3, L2Zn3, L2Mg3, and L2Cd3 (4−8) are similar; two trihydrazone ligands are involved in coordination to hold the three metal ions in a linear fashion. Each of the trishydrazone ligands behaves as a trianionic hexadentate ligand providing three imino and three phenolic oxygen atoms for coordination to the metal ions. The coordination environment around the two terminal metal ions is similar (3N, 3O) while the central metal ion has a 6O coordination environment. Third-order non-linear optical properties of these compounds as measured by their two-photon absorption (TPA) cross section reveals that while 1 does not possess obvious TPA activity, complexes 2 (3213 GM) and 4 (3516 GM) possess a large TPA cross section at 770 nm.

     BibTeX: @article{chandrasekharSynthesisStructureTwoPhoton2011,
      title = {Synthesis, {{Structure}}, and {{Two}}-{{Photon Absorption Studies}} of a {{Phosphorus}}-{{Based Tris Hydrazone Ligand}} ({{S}}){{P}}[{{N}}({{Me}}){{N}}═{{CH}}-{{C6H3}}-2-{{OH}}-4-{{N}}({{CH2CH3}})2]3 and {{Its Metal Complexes}}},
      volume = {49},
      issn = {0020-1669},
      url = {https://doi.org/10.1021/ic901531e},
      doi = {10/bvqgfp},
      number = {9},
      journaltitle = {Inorg. Chem.},
      urldate = {2019-08-14},
      date = {2010-05-03},
      pages = {4008-4016},
      author = {Chandrasekhar, Vadapalli and Azhakar, Ramachandran and Murugesapandian, Balasubramanian and Senapati, Tapas and Bag, Prasenjit and Pandey, Mrituanjay D. and Maurya, Sandeep Kumar and Goswami, Debabrata}
    }
    

21. Probing the Ultrafast Solution Dynamics of a Cyanine Dye in an Organic Solvent Interfaced with Water. T. Goswami, S. K. K. Kumar, A. Dutta, and D. Goswami, J. Phys. Chem. B 113(51), 16332–16336 (2009) [Abstract] [PDF] [BibTeX]

    Abstract: Dependence of ultrafast dynamics on the excited state evolution and ground state recovery of a cyanine dye (IR125) in dichloromethane (DCM) solvent interfaced with neat water is presented. We use degenerate pump−probe transient absorption spectroscopy to show that the excited-state dynamics of the dye molecule is strongly dependent on the position of the measurements from bulk DCM solution to the solution near the water layer. The decay component of the transient corresponding to the excited state lifetime increases from bulk DCM solution to its interface with water. Such results show that the effect of the presence of water layer over the dye solution in DCM extends several micrometers, indicating the surfactant nature of the IR125 molecules, and provides us a measure of the penetration of water into the DCM layer. The initial ultrafast decay component (coherent spike) directly correlates to the pulse-width of our near-transform limited pulses used in these experiments. This approach of measuring the excited state decay of a dye across an immiscible liquid interface can provide important characteristics of microtransport across such interfaces.

     BibTeX: @article{goswamiProbingUltrafastSolution2011,
      title = {Probing the {{Ultrafast Solution Dynamics}} of a {{Cyanine Dye}} in an {{Organic Solvent Interfaced}} with {{Water}}},
      volume = {113},
      issn = {1520-6106},
      url = {https://doi.org/10.1021/jp903753u},
      doi = {10/dc3b67},
      number = {51},
      journaltitle = {J. Phys. Chem. B},
      urldate = {2019-08-14},
      date = {2009-12-24},
      pages = {16332-16336},
      author = {Goswami, Tapas and Kumar, S. K. Karthick and Dutta, Aveek and Goswami, Debabrata}
    }
    

22. Spectrally Resolved Photon Echo Spectroscopy of Zn(II), Co(II) and Ni(II)–Octaethyl Porphyrins. S. K. Karthick Kumar, V. Tiwari, T. Goswami, and D. Goswami, Chemical Physics Letters 476(1), 31–36 (2009) [Abstract] [PDF] [BibTeX]

    Abstract: Spectrally resolved femtosecond three-pulse photon echo signal from some metal–octaethyl porphyrins (OEPs) like Zn(II)–OEP, Ni(II)–OEP, Co(II)–OEP is reported. Excited state dynamics is studied by time evolving photon echo spectra for different values of coherence and population relaxation times. Dependence on the spectrally resolved photon echo spectra on varying metal center is analyzed. For all these metallo-porphyrins, the electronic relaxation timescale is found to be limited by our laser pulsewidth of 50fs whereas the timescale for intramolecular vibrational relaxation, occurring within the Q00 band was found to be over a picosecond for Co(II)–OEP and Ni(II)–OEP and within a picosecond for Zn(II)–OEP.

     BibTeX: @article{karthickkumarSpectrallyResolvedPhoton2011,
      title = {Spectrally Resolved Photon Echo Spectroscopy of {{Zn}}({{II}}), {{Co}}({{II}}) and {{Ni}}({{II}})–Octaethyl Porphyrins},
      volume = {476},
      issn = {0009-2614},
      url = {http://www.sciencedirect.com/science/article/pii/S0009261409006666},
      doi = {10/fpmh7d},
      number = {1},
      journaltitle = {Chemical Physics Letters},
      urldate = {2019-08-14},
      date = {2009-07-07},
      pages = {31-36},
      author = {Karthick Kumar, S. K. and Tiwari, Vivek and Goswami, Tapas and Goswami, Debabrata}
    }
    

23. Control of Laser Induced Molecular Fragmentation of N-Propyl Benzene Using Chirped Femtosecond Laser Pulses. T. Goswami, S. K. Karthick Kumar, A. Dutta, and D. Goswami, Chemical Physics 360(1), 47–52 (2009) [Abstract] [PDF] [BibTeX]

    Abstract: We present the effect of chirping a femtosecond laser pulse on the fragmentation of n-propyl benzene. An enhancement of an order of magnitude for the relative yields of C3H3+ and C5H5+ in the case of negatively chirped pulses and C6H5+ in the case of positively chirped pulses with respect to the transform-limited pulse indicates that in some fragmentation channel, coherence of the laser field plays an important role. For the relative yield of all other heavier fragment ions, resulting from the interaction of the intense laser field with the molecule, there is no such enhancement effect with the sign of chirp, within experimental errors. The importance of the laser phase is further reinforced through a direct comparison of the fragmentation results with the second harmonic of the chirped laser pulse with identical bandwidth.

     BibTeX: @article{goswamiControlLaserInduced2011,
      title = {Control of Laser Induced Molecular Fragmentation of N-Propyl Benzene Using Chirped Femtosecond Laser Pulses},
      volume = {360},
      issn = {0301-0104},
      url = {http://www.sciencedirect.com/science/article/pii/S0301010409001219},
      doi = {10/b2h79c},
      number = {1},
      journaltitle = {Chemical Physics},
      urldate = {2019-08-14},
      date = {2009-06-12},
      pages = {47-52},
      author = {Goswami, Tapas and Karthick Kumar, S. K. and Dutta, Aveek and Goswami, Debabrata}
    }