DISTRIBUTIONS OF ROVIBRATIONAL STATES OF SECONDARY PRODUCT NO X-2-PI FROM PHOTODISSOCIATION OF NITRIC ACID AT 193 NM

摘要

The distributions of vibrational, rotational, spin-orbit and lambda-doublet states of nascent NO are obtained using: the A (2) Sigma-X (II)-I-2 transition via the technique of laser-induced fluorescence. NO is produced mainly from secondary dissociation of fragment NO2 from nitric acid after photolysis at 193 nm. According to the measured distribution the partition of energy in NO X (II)-I-2 is calculated to be similar to 840 cm(-1) in vibration and similar to 1410 cm(-1) in rotation. The spin-orbit state (II1/2)-I-2 Of NO is populated about twice of that in (II3/2)-I-2 for the vibrational levels upsilon=0, 1, and 2. The measured populations of vibrational states upsilon=0, 1, and 2 are 0.75, 0.19, and 0.07, respectively; these populations agree with results calculated with the statistical model, prior theory. The distributions of rotational states of NO X (II)-I-2 for these three vibrational levels have single maxima of Gaussian shape. The experimental data indicate that although NO2, produced photochemically from nitric acid, was proposed to be in an electronically excited state, the state distributions of NO from unstable NO2 agree with chose from NO2 excited with monochromatic light in the UV-vis range after averaging for a broad distribution of internal energy. In the UV-vis range of excitation the NO fragment dissociates from the ground electronic surface of NO2. Hence, this unknown electronic state of NO, is expected to be coupled to the ground electronic surface then leading to dissociation. (C) 1997 American Institute of Physics. [References: 41]