Time-dependent photoionization of azulene: Optically induced anisotropy on the femtosecond scale

We measure the photoionization cross-section of vibrationally excited levels in the S2 state of azulene by femtosecond pump-probe spectroscopy. At the wavelengths studied (349-265 nm in the pump) the transient signals exhibit two distinct and well-defined behaviours: (i) Short-term (on the order of a picosecond) polarization dependent transients and (ii) longer (10 ps - 1 ns) time-scale decays. This letter focuses on the short time transient. In contrast to an earlier study by Diau et al.22 [J. Chem. Phys. 110 (1999) 9785.] we unambiguously assign the fast initial decay signal to rotational dephasing of the initial alignment created by the pump transition.Comment: Chemical Physics Letters (2008

ULTRAFAST TRANSIENT SOLVATION OF POLAR DYE MOLECULES IN SIMPLE POLAR SOLVENTS

$^{1}$ M.A. Kahlow. T.J. Kang and P.F. Barbara. J. Chem. Phys. 88. 2372 (1988); M.A. Kahlow. W. Jarzeba. T.P. DuBruil and P.F. Barbara. Rev. Sci. Instrum. (in press). $^{2}$ E.W. Castner. G.R. Fleming and B. Bagchi. Chem. Phys. Lett. (in press). $^{3}$ P.G. Wolynes. J. Chem. Phys. 86. 5133 (1987).Author Institution: Department of Chemistry, University of Minnesota,Recently we constructed a time resolved fluorescence apparatus with a resolution of less than 300 femtoseconds1. We have used this instrument to measure the microscopic solvation dynamics of three simple polar solvents (propylene carbonate, propiontrile, and methanol) by observing the time resolved fluorescence from coumarin 152. The solvation rates are non-singly exponential, with components both shorter and longer than the longitudinal relaxation times r1 of the solvents. Results will be discussed in terms of several recent theoretical $models^{2-3}$

Insights into the structure of cyclohexane from femtosecond degenerate four-wave mixing spectroscopy and ab initio calculations

In this paper, we report the use of femtosecond time-resolved degenerate four-wave mixing rotationally resolved spectroscopy to obtain very accurate structural information on the symmetric top cyclohexane. Apart from highlighting the versatility of this method in determining accurate structures of large and complex molecules without dipole moment, the present study also details the comparison of the experimentally determined rotational constant B-0 with that obtained from high-level ab initio calculations. The theoretical calculations, which were carried out at both the second-order Moller-Plesset (MP2) and coupled-cluster with single, double, and perturbative triple substitutions [CCSD(T)] levels of theory, also take into account vibrational averaging effects. A detailed investigation of the vibrational averaging effects reveals that the corrections emerge from only the six highly symmetric A(1g) modes, a justification of which is provided by an analysis of these modes.X112120sciescopu

Unraveling the internal dynamics of the benzene dimer: a combined theoretical and microwave spectroscopy study

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