PHOTODISSOCIATION OF CH STRETCH OVERTONE EXCITED CH3CL AND CHD2CL (V(CH)=5) - CL SPIN-ORBIT BRANCHING AND ATOMIC FRAGMENT YIELDS

The photodissociation dynamics of CH3Cl and CHD2Cl excited through the ir respective fourth C-H stretch overtone transitions have been invest igated by detection of ground state Cl(P-2(3/2)), spinorbit excited Cl (P-2(1/2)), H, and D atomic fragments by 2+1 resonance enhanced multip hoton ionization in a time-of-flight mass spectrometer. The yield of a tomic Cl fragments from the vibrationally mediated photodissociation o f CHD2Cl is significantly less than for CH3Cl, more than can be accoun ted for from differences in the cross sections for overtone excitation . This suggests that state mixing leads to a greater amplitude of the wave function of the vibrationally excited level along the dissociatio n coordinate in CH3Cl than in CHD2Cl. The observed differences in the Cl spin-orbit branching in the photolysis of ground state versus vibra tionally excited molecules are ascribed to differences in the nuclear dissociation dynamics, rather than access to other excited electronic states. The relative yields of H and D atoms from the photodissociatio n of ground and vibrationally excited CHD2Cl are also reported and dis cussed. (C) 1998 American Institute of Physics. [S0021-9606(98)01542-6 ].