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  • 1
    Electronic Resource
    Electronic Resource
    Time resolved dynamics of isolated molecular systems studied with phase-locked femtosecond pulse pairs (1990)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 93 (1990), S. 856-857 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.459456
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  • 2
    Electronic Resource
    Electronic Resource
    Real-time clocking of bimolecular reactions: Application to H+CO2 (1990)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 92 (1990), S. 5239-5259 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: An experimental methodology is described for the real-time clocking of elementary bimolecular reactions, i.e., timing the process of formation and decay of the collision complex. The method takes advantage of the propinquity of the potential reagents in a binary van der Waals (vdW) "precursor'' molecule. An ultrashort pump laser pulse initiates the reaction, establishing the zero-of-time (e.g., by photodissociating one of the component molecules in the vdW precursor, liberating a "hot'' atom that attacks the nearby coreagent). A second ultrashort, suitably tuned, variably delayed probe laser pulse detects either the intermediate complex or the newly born product. From an analysis of this temporal data as a function of pump and probe wavelengths, the real-time dynamics of such a "van der Waals-impacted bimolecular (VIB)'' reaction can be determined. Chosen as a demonstration example is the VIB reaction H+CO2→HOCO
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.458531
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  • 3
    Electronic Resource
    Electronic Resource
    Femtosecond polarization spectroscopy: A density matrix description (1994)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 100 (1994), S. 1823-1839 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A density matrix treatment of the time evolution of the third order polarization response describing the optical heterodyne detected (OHD) transient birefringence and dichroism excited by ultrafast pulses is given. The relationship between frequency domain (Raman scattering) and time domain (pump–probe) spectroscopies is revealed by this pathway explicit description. Constructive and destructive interferences between time evolution density matrix pathways account for the respective strong birefringent and weak dichroic ground state nuclear response when the pulses are electronically nonresonant. However, for electronically resonant chromophores, the dichroic response is larger than the corresponding birefringent response due to constructive and destructive interferences respectively between density matrix time evolution histories. No such interferences contribute to spontaneous Raman scattering. The relative magnitude of the resonant dichroic and birefringent responses is pulse width dependent in the fast pulse limit and dependent on the relative rates of optical dephasing and ground state nuclear motion in the rapid optical dephasing limit. The spatial interpretation of the ground and excited state OHD polarization responses is given within the context of this polarization approach and the familiar Maker–Terhune notation. These relationships between time and frequency domain spectroscopies are illustrated by the observed OHD birefringence and dichroism and the spontaneous Raman spectra of both a nonresonant liquid (chloroform) and a resonant solution (I2 in n-hexane).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.467252
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  • 4
    Electronic Resource
    Electronic Resource
    Optical dephasing on femtosecond time scales: Direct measurement and calculation from solvent spectral densities (1995)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 102 (1995), S. 4027-4036 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The connection between dephasing of optical coherence and the measured spectral density of the pure solvent is made through measurements and calculations of photon echo signals. 2-pulse photon echo measurements of a cyanine dye in polar solvents are presented. Signals are recorded for both phase matched directions enabling accurate determination of the echo signal time shift. Echo signals are calculated by two approaches that employ the response function description of nonlinear spectroscopy; (i) a single Brownian oscillator line shape model, and (ii) the line shape obtained using the solvent spectral density. The strongly overdamped Brownian oscillator model incorporates only a single adjustable parameter while the experimental data present two fitting constraints. The second model incorporates the measured solvent spectral density. Both give very good agreement with the experimental results. The significance of the second method lies in this being a new approach to calculate nonlinear spectroscopic signals, for comparison with experimental data, that uses directly the measured spectrum of equilibrium fluctuations of the solvent. This approach also provides a better conceptual perspective for deriving insight into the nature of the solute–solvent coupling mechanism. Comparing the parameters for the strength of interaction in a variety of polar solvents it is found that the coupling involves the solvent polarizability and not the solvent polarity. The interaction mechanism cannot be deduced from the Brownian oscillator calculations. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.468531
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  • 5
    Electronic Resource
    Electronic Resource
    Direct picosecond time resolution of unimolecular reactions initiated by local mode excitation (1986)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 84 (1986), S. 1932-1933 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.450443
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  • 6
    Electronic Resource
    Electronic Resource
    Ultrafast molecular relaxation of isolated stilbene: measurements by picosecond pump-probe techniques (1985)
    s.l. : American Chemical Society
    The @journal of physical chemistry 〈Washington, DC〉 89 (1985), S. 894-896 
    Details
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/j100252a004
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  • 7
    Electronic Resource
    Electronic Resource
    Femtosecond photofragment spectroscopy of the reaction iodine cyanide (ICN) .fwdarw. cyanogen (CN) + atomic iodine (1985)
    s.l. : American Chemical Society
    The @journal of physical chemistry 〈Washington, DC〉 89 (1985), S. 5141-5143 
    Details
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/j100270a001
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  • 8
    Electronic Resource
    Electronic Resource
    Nonlinear polarization description of phase-locked pulse-pair spectroscopy (1992)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 97 (1992), S. 4704-4713 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The recently demonstrated technique of optically phase-locked pulse-pair (PLPP) excited spontaneous emission is described by a third-order perturbative density matrix approach. A nonlinear polarization description shows how PLPP spectroscopy depends on all the relevant material dephasing time scales. The time and frequency integrated resonance spontaneous emission consists entirely of resonance fluorescence, and is derived exclusively from excited-state population decay terms, i.e., diagonal second-order density-matrix elements. These third-order polarization results are proportional to the previously derived linear polarization expressions found to describe the observed PLPP I2 vapor emission. The nonlinear treatment allows a comparison of this technique to other forms of ultrafast pump–probe spectroscopies such as transient absorption and photon echo techniques. The role of impulsively prepared coherences is clearly described by this analysis. The effect of pulse duration, relative to material dephasing times, is explored for relaxation given by the optical Bloch equations. The most significant differences between a linear and nonlinear polarization treatment occur for pulse durations greater than the optical dephasing time or when excited state population and coherence decays are of the order of rovibrational periods. A fluorescence line narrowing effect, due to short pulse excitation, is predicted.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.463872
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  • 9
    Electronic Resource
    Electronic Resource
    Heterodyne-detected time-domain measurement of I2 predissociation and vibrational dynamics in solution (1992)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 96 (1992), S. 5544-5547 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.462693
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  • 10
    Electronic Resource
    Electronic Resource
    Fluorescence-detected wave packet interferometry. II. Role of rotations and determination of the susceptibility (1992)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 96 (1992), S. 4180-4194 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The recently developed technique of time-resolved spectroscopy with phase-locked optical pulse pairs is further explored with additional experimental data and more detailed comparison to theory. This spectroscopic method is sensitive to the overall phase evolution of an optically prepared nuclear wave packet. The phase locking scheme, demonstrated for the B←X transition of gas phase molecular iodine, is extended through the use of in-quadrature locked pulses and by examination of the dispersed fluorescence signal. The excited state population following the interaction with both pulses is detected as the resultant two-field-dependent fluorescence emission from the B state. The observed signals have periodically recurring features that result from rovibrational wave packet dynamics of the molecule on the excited state electronic potential energy curve. Quantum interference effects cause the magnitude and sign of the periodic features to be strongly modulated. The two-pulse phase-locked interferograms are interpreted with first order time-dependent perturbation theory. Excellent agreement is found between the experimental interferograms and those calculated from literature values of the parameters governing the electronic, vibrational and rotational structure of I2. A relationship between the phase-locked interferograms and the time-dependent linear susceptibility is obtained. The in-phase and in-quadrature phase-locked interferograms together provide a complete record of the optical free induction decay. Thus by combining the in-phase and in-quadrature data, we obtain the contributions to both the absorptive and dispersive linear susceptibilities arising from transitions within the pulse spectrum.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.462837
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