PHOTODISSOCIATION DYNAMICS OF HN3(DN3)-NU-]H(D)+N-3(H)

The photolysis of HN3/DN3 to give H/D and N-3 is investigated at diffe rent photolysis wavelengths: 266, 248, 222, 193 and 122 nm. Nascent H/ D atoms are characterized via Doppler and polarization spectroscopy us ing laser-induced fluorescence in the VUV. The following quantum yield s have been found: phi(H-N3) (266 nm) = 0.04, phi(H-N3) (248 nm) appro ximate to phi(D-N3) (248 nm) = 0.20, and phi(H-N3) (193 nm) approximat e to phi(D-N3) (193 nm) = 0.14. At a photolysis wavelength of 266 nm m ost of the available energy goes into product translation, [E(kin)] = 5820 cm(-1), while the internal energy of the N-3 fragment is fairly l ow, [E(int)(N-3)] = 1250 cm(-1). At 248 nm the values are 6640 and 315 0 cm(-1), respectively. Thus additional excess energy is preferentiall y released as internal energy of the N-3 radical. This trend is less p ronounced when the excitation wavelength is set to 222 or 193 nm. At 1 22 nm the kinetic energy of the photofragments is smaller than in the 193 nm experiment At 266 and 248 nm the spatial distribution of the ph otofragments is described by a strongly negative anisotropy parameter indicating a definite preference for a perpendicular alignment of the electronic transition moment and the recoil velocity vector. At 222 an d 193 nm the anisotropy parameter is close to zero, while the VUV phot olysis results in a slightly positive anisotropy parameter. These expe rimental findings indicate that the access to different electronic sta tes of HN3/DN3 is gained as the photolysis wavelength is varied from 2 66 to 122 nm.