Selective Photodissociation of Ammonia at 000 and 201 Bands

Abstract

The photofragnentation dynamics of ammonia molecules following pulsed UV laser excitation of ground state to the two lowest levels ν′2 = 0 and 1 (ν2 vibrational mode) of their ?1(A"2) electronic excited state has been investigated by monitoring thetime-of-flight spectra of the nascent H-atom products. The spectra confirm recent revised estimates of the quantity D00(H-NH2) = 4.645 eV and reveals that the majority of the accompanying NH2 (X2B1) fragments are formed vibrationally unexcited, but with high levels of rotational excitation specifically concentrated about the a-inertial axis. The NH2(X) fragments resulting from photodissociation via the ν′2 = 1 level of NH3(?) carry a higher level of internal excitation and show an inverted population distribution over the N = Ka rotational levels.