Systematics of the gradient on the resonant core-hole state

Abstract

Systematics of the gradient on the resonant core-hole state in the Franck-Condon region were investigated theoretically. The steepest gradient for a target bond in the resonant core-excited states becomes more negative with increasing sum of atomic numbers of the atom in the bonded pair and increasing bond order for the associated chemical bond. Gradients for molecules that include conjugated double bonds such as butadiene and hexatriene were also examined at the lowest core-hole state. The gradients for the double bond become negative while that those for the single bond become positive with few exceptions, suggesting that a fragment from a target molecule gains its initial momentum at the multiple bond.

Chemical bond elongation following core-excitation of ammonia: resonant Auger spectra calculation

“…Bond lengths at the ground state shorten with increasing the atomic number in target molecules, and gradients become more negative. These are interpreted by the nuclear-nuclear repulsion between a core-hole and a hydrogen atom and by the excitation to the unoccupied orbital for the target chemical bond [27].…”

“…A detailed computational procedure of Auger decay spectra has been described elsewhere [17,26,27]. Briefly, a set of core-hole molecular orbitals (MO's) was obtained by the above DFT calculations.…”

Site-selective bond scission of methylbenzoate following core excitation

“…Previously Takahashi et al examined the relationship between several chemical bonds and the gradient of the resonant core-hole state in the Frank-Condon region. 33 In that study, they derived that the gradient of the resonant core-hole state in the Frank-Condon region becomes more negative with the increasing sum of atomic numbers of bonding pair atoms. Along with this relation, nuclear motion of the C-C bonds on the resonant core-hole state cannot be expected effectively.…”

“…Theoretical approaches can help to understand the reaction mechanisms following core-excitation. [31][32][33] Takahashi and coworkers reported the ion desorption reaction of PMMA thin films and explained that the reason of bond scission acceleration for a C-O bond is the excitation to resonant state of anti-bonding character in respect of the targeted chemical bond. Using core-excited state dynamics simulation, the target chemical bond scission can be shown explicitly to occur.…”

“…Furthermore, Takahashi et al examined the gradient of the potential energy surface of several resonant excited states for various chemical bonds, and derived some simple rules for chemical bond scission following core-excitation. 33 In the present study, site-specific chemical reactions of methylbenzoate are examined following core excitation at C and O K-edges. Methylbenzoate is a volatile compound at room temperature and atmospheric pressure and possesses the methylacetate functional group (-COOCH 3 ), which is also included in the PMMA thin film, and a benzyl group as a large energy relaxation buffer.…”