Tunable picosecond spectroscopy for detection of nitric oxide

Abstract

Nitric oxide (NO) is a major chemical byproduct of many photochemically active nitrogen-containing compounds. As a prototypical free radical with a very well characterized high-resolution spectrum, NO provides a standard spectroscopic fingerprint for indirect quantitative analysis and detection of a number of low vapor pressure nitroaromatic compounds in air through either direct photochemical decomposition of a parent molecule or from its relatively high vapor pressure chemical constituents. In this paper, we will discuss applications of picosecond laser spectroscopy for measurements and detection of NO and the nascent NO generated from photolysis of nitrobenzene. We will give a general overview of our tunable picosecond laser and detection system that we routinely use for probing and exciting the NO gamma band. This broad wavelength tuning capability of our laser allows us to set up pump-probe type experiments for detecting blue shifted rovibronic bands and probing the relative population distribution for NO. In all cases, experiments were performed using UV laser pulses of duration less than 20 ps. Also, we studied the effect of N₂ collisions on the photoframentation spectrum of nitrobenzene in 1000 mbar of N₂ buffer gas.