ISSN:
1089-7690
Source:
AIP Digital Archive
Topics:
Physics
,
Chemistry and Pharmacology
Notes:
The early quantum dynamics following the B(3Π0u+)←X photoexcitation of I2 in large rare gas clusters is studied and the resonance Raman spectrum of these systems is calculated by a novel time-dependent quantum mechanical simulation approach. The method used is the classically based separable potential (CSP) approximation, in which classical molecular dynamics simulations are used in a first step to determine an effective time-dependent separable potential for each mode, then followed by quantum wavepacket calculations using these potentials. In the simulations for I2(Ar)n and I2(Xe)n, with n=17, 47, all the modes are treated quantum mechanically. The Raman overtone intensities are computed from the multidimensional time-dependent wavepacket for each system, and the results are compared with experimental data on I2 in Ar matrices and in liquid Xe. The main findings include: (i) Due to wavepacket dephasing effects the Raman spectra are determined well before the iodine atoms hit the rare gas "wall'' at about 80 fs after photoexcitation. (ii) No recurrencies are found in the correlation functions for I2(Ar)n. A very weak recurrence event is found for I2(Xe)n. (iii) The simulations for I2(Ar)17 (first solvation layer) and for I2(Ar)47 (second solvation shell) show differences corresponding to moderate cluster size effects on the Raman spectra. (iv) It is estimated that coupling to the B″(1Π1u) state or to the a(1g) state have a small effect on the Raman intensities. (v) For I2(Ar)47, the results are in very good quantitative agreement with I2/Ar matrix experiments. The I2(Xe)n results are in qualitative agreement with experiments on I2 in liquid Xe. The reported calculations represent a first modeling of resonance Raman spectra by quantum dynamical simulations that include all degrees of freedom in large systems, and they demonstrate the power of the CSP method in this respect. © 1996 American Institute of Physics.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1063/1.471678
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