Dynamical spectroscopy of many-body interactions. Coherent vibrations and predissociation of I2(B) in solid Kr

Abstract

I₂(B) isolated in Kr matrices is prepared between 560 and 490 nm, and probed via the f(0_g⁺)â†� B(0_u⁺) transition, with a time resolution of 150–200 fs. It is shown that the prepared vibrational population evolves coherently and decays in amplitude owing to predissociation. Where the population is prepared on a single electronic surface, near λ= 550 nm, the experimental signal can be reproduced quantitatively via classical simulations. The analysis yields: (a) the location of the f(0_g⁺) ion-pair state, the electronic solvation energy of which the Kr is determined as 4300 cm^–1, (b) the characterization of vibrational relaxation dynamics, which near v= 20 reaches a limiting decay rate of 60 cm^–1 per period and (c) a direct measurement of the host-induced electronic predissociation lifetime of 4.5 ps. With the assumption that this is due to B→ a curve crossing, an electronic matrix element of 54 ± 7 cm^–1 is implied in solid Kr. The solid-state results are discussed in relation to measurements in other phases: gas, liquid and clusters. The example is used as an illustration of dynamical spectroscopy, as time-dependent resonances which can be interpreted through analysis of the underlying many-body dynamics.