PHOTODISSOCIATION OF HNO3 AT 193 NM - NEAR-INFRARED EMISSION OF NO DETECTED BY TIME-RESOLVED FOURIER-TRANSFORM SPECTROSCOPY

Rotationally resolved emission of NO, produced from photolysis of HNO3 at 193 nm, in the near infrared region (8900-9300 cm(-1)) was recorde d with a step-scan Fourier-transform interferometer at a resolution of 0.1 cm(-1). The emission is assigned as NO D (2) Sigma(+) -A (2) Sigm a(+) (nu',nu'')=(0,0) band with rotational states N'=17-42. Emission f rom selective rotational states of NO D (2) Sigma(+) was observed when HNO3 was photolyzed with an ArF excimer laser having a narrow bandwid th approximate to 0.01 nm. The experimental results indicate that the D (2) Sigma(+) state of NO is formed via absorption of another 193 nm photon by NO (nu''=1) in the ground electronic state. The measured dis tribution of intensity implies that NO is produced highly rotationally excited; the most likely mechanism for formation of NO is from the un stable NO2 fragment undergoing secondary dissociation. (C) 1995 Americ an Institute of Physics.