The mechanism of the spin-forbidden photofragmentation of the NCO radical

Conference · Fri Dec 31 04:00:00 EST 1993

OSTI ID:141387

Alexander, M H; Werner, H J

The authors shall report the results of ab initio MCSCF+CI calculations with large atomic orbital bases of the topology of the potential surfaces relevant to the photofragmentation of NCO. At energies below the N({sup 2}D) + CO asymptote, NCO in the {tilde A}{sup 2}{Sigma}{sup +} and {tilde B}{sup 2}{Pi} states can decompose only by a spin-forbidden route, by way of the crossing with the repulsive quartet surface which correlates asymptotically with the lower N({sup 4}S) + CO channel. The ab initio calculations demonstrate that there exists a crossing between the {tilde A}{sup 2}{Sigma}{sup +} and {tilde B}{sup 2}{Pi} states of NCO, which lies close to the equilibrium geometry of the {tilde B} state, and only slightly higher in energy than the minimum of this state. It is this crossing which facilitates the formation of dissociation products, observed by Neumark and co-workers, via the following mechanism: NCO({sup 2}{Pi},A{prime}) {yields} NCO({sup 2}{Sigma}{sup +}, {nu}) {yields} NCO({sup 4}A{double_prime}) {yields} N({sup 4}S) + CO (X{sup 1}{Sigma}{sup +}). This crossing also explains the dramatic fall in the radiative lifetime of the {tilde B} state observed by Crosley and co-workers.

• OSTI ID: 141387
• Report Number(s): CONF-930304--; CNN: Grant DAAL03-91-G-0129
• Country of Publication: United States
• Language: English

Related Subjects

40 CHEMISTRY
CARBONYL RADICALS
CHEMICAL REACTION KINETICS
DISSOCIATION
FORBIDDEN TRANSITIONS
NITROGEN OXIDES
PHOTOCHEMISTRY
PHOTOLYSIS
PHYSICAL CHEMISTRY