Photodissociation multiple electronic states

I. H2CO Photodissociation Participation of Multiple Electronic States... 

A second illustrative example of the utility of TRPES and TRCIS for studying complex molecular photodissociation dynamics that involve multiple electronic state is the case of the weakly bound cis-planar C2V nitric oxide dimer [174], The weak (Do = 710cm-1) 1 A ground-state covalent bond is formed by the pairing of two singly occupied ji orbitals, one from each NO(X2II) monomer. The very intense UV absorption spectrum of the NO dimer appears... 

Multiple pathways to the same product channel therefore occur via nonadiabatic transitions that lead from the initial electronic state to at least one other electronic state before converging on the product asymptote. Two examples are presented in this chapter the photodissociations CH2O —> H + HCO and H2O H + OH. There is evidence of similar effects in the photodissociation HNCO H + NCO [13]. 

The work of Fu 3 and co-workers (2,5-7,34) has shown that Cr (CO)5, Mn(CO)5 and Fe(C0)4 return to the lowest electronic states of the initially excited multiplicity within several hundred femtoseconds of the photodissociation of the parent carbonyl. This timescale precludes a spin-orbit induced change from the low-spin manifold and anticipates the accessibility of a conical intersection seam to facilitate radiationless population transfer to the ground state. 

Hydroxyl radical (OH) is a key reactive intermediate in combustion and atmospheric chemistry, and it also serves as a prototypic open-shell diatomic system for investigating photodissociation involving multiple potential energy curves and nonadiabatic interactions. Previous theoretical and experimental studies have focused on electronic structures and spectroscopy of OH, especially the A2T,+-X2n band system and the predissociation of rovibrational levels of the M2S+ state,84-93 while there was no experimental work on the photodissociation dynamics to characterize the atomic products. The M2S+ state [asymptotically correlating with the excited-state products 0(1 D) + H(2S)] crosses with three repulsive states [4>J, 2E-, and 4n, correlating with the ground-state fragments 0(3Pj) + H(2S)[ in... 

Fig. 6. The optical absorption spectrum and the electronic structure of Mn2". (a) Experimental data, where a photodissociation action spectrum of Mn2 was measured by observing Mn" " photofragment, (b) The spectrum calculated by a hybrid-type density-functional method. The bars show oscillator strengths the solid line a spectral profile, (c) Density-of-states profiles of the majority and the minority spin electrons obtained by the same theoretical calculation. The shadows indicate occupied electronic levels. The manganese dimer ion, Mn2 ", was shown to have a spin multiplicity of twelve with a bond length of 3.01 A. ...

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