Vibrational population dynamics of the HgI photofragment in ethanol solution

Abstract

The vibrational population dynamics of HgI fragments in ethanol solution, resulting from the 320 nm photolysis of HgI 2 , are examined both experimentally and by a simulation. The experiments reveal an HgI population distribution which rapidly relaxes toward equilibrium. At the earliest times, the HgI exhibits vibrational coherent wave-packet motion that dephases with a time constant of ca. 1 ps. These data are used to gain insight into the character of the solvated potential energy curves. The population relaxation was adequately reproduced by master equations which were formulated to incorporate the HgI anharmonicity and a solvent frequency dependent friction. This treatment characterizes the spontaneous vibrational relaxation timescale for the nЉϭ1→0 transition to be ca. 3 ps, and is used to identify the relaxation rate constants for all other HgI level pairs. The simulations estimate that the initial excess energy of HgI is centered at nЉХ10 which corresponds to a total excess energy of ca. 1050 cm Ϫ1 .

Dynamical Approach to Vibrational Relaxation

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Time resolved infrared studies of C-H bond activation by organometallics

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Ultrafast One-Photon (232 vs 266 nm) Bond-Selective Photochemistry of Bromoiodomethane (CH2BrI) in Solution

“…The formation of these bands is faster than our instrumental response time limited by solvent coherent artifact to about 400 fs. The 275-and 240-nm absorption bands are ascribed to a I·CH 3 CN charge-transfer complex (formation time in polar solvents, ≤ 0.3 ps, [4]) and a CH 2 Br· radical, [5], respectively. The absorption of CH 2 Br· and I·CH 3 CN shows no change up to 500 ps, suggesting that these species once formed following excitation of CH 2 BrI do not collapse within 500 ps to produce either the parent or the CH 2 Br-I isomer molecules.…”