On the semiclassical dissociation yields of the doubly excited states of H2

Production of excited atomic hydrogen and deuterium from H2and D2photodissociation

“…Processes (1), (2), (3) and (4) correspond, respectively, to the production of a singly excited molecule which subsequently dissociates, direct non-resonant molecular ionization followed by prompt dissociation, production of doubly excited "Q" states embedded in the continuum which can either autoionize and dissociate or promptly dissociate into a variety of possible photofragments and, fi nally, prompt double ionization. Understanding processes (1)-(4)is aided by reference to fi gure 1.…”

“…Photodissociation of H 2 is the simplest chemical reaction, yet our theoretical understanding of it is incomplete [1][2][3][4][5][6][7]. The photodissociation process involves the correlated motion of strongly interacting particles, often having large potential and/or kinetic energy.…”

Formation of metastable atomic hydrogen in the 2sstate from symmetry-resolved doubly excited states of molecular hydrogen

“…Thus, a consensus that the precursor state of the fast H(2s) fragment is the Q 2 1 u (1) state has been developed. Because the state was also known as the main contributor to the cross section for the H(2p) atom formation [16][17][18][19], the Q 2 1 u (1) state has been considered to dissociate into H(2s) + H(2p). However, this conclusion needs to be re-examined since (i) the theoretical potential energies and resonance widths of the doubly excited states of H 2 by the recent calculation with large configuration bases [6] differ from those by the former calculation [15] and (ii) the velocity distributions of H(2s) fragments depend on the electron impact energy [20], showing a possibility of contributions from the neutral and ionic molecular states other than the Q 2 1 u (1) state in the electron collision experiment by Misakian and Zorn.…”

Production of excited atomic hydrogen and deuterium from H2 and D2 photodissociation

“…Since photon absorption is practically an instantaneous process, the molecular target can be thought of as making a "vertical (Franck-Condon) transition," whose height corresponds to the incident photon energy. However, the subsequent evolution of the system through processes (1)- (4) implies that the electronic and nuclear motions cannot be considered separately, and that the assumption of adiabatic nuclear motion during dissociation is no longer appropriate. While the photodissociation of H 2 is fundamental, it is not simple, as is apparent from the cappellini-like potential energy diagram of fi gure 1.…”

“…However, previous attempts [3,4,6,[13][14][15][16] to evaluate the photodissociation cross section σ d have made use of the simple empirical formula σ d (E) = χ d σ a (E), where σ a is the absorption cross section evaluated in the Franck-Condon approximation and χ d is the dissociation yield or survival probability. The latter quantity has been either estimated [13] or calculated semiclassically [3,4] assuming that it is independent of the photon energy. This procedure neglects interferences between autoionization and direct ionization, as well as between different doubly excited states.…”