Tunable Picosecond Spectroscopy for Detection of NO

Nitric oxide (NO) is a major chemical byproduct of many photochemically active nitrogen-containing compounds. As a prototypical free radical with very well characterized high resolution spectrum, NO provides a standard spectroscopic fingerprint for indirect quantitative analysis and detection of a number of low vapor 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 application of picosecond laser spectroscopy for measurements and detection of NO and the nascent NO generated from photolysis. 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 in the 200 - 300 nm wavelength range. This broad wavelength tuning capability of our laser allows us to set up pump-probe type experiments for detecting blue-shifted rovibronic bands, transferring population via stimulated emission pumping, and probing the relative population distribution for NO. In all cases, experiments were performed using laser pulses with a duration of less than 10 ps. As a result, our measurements could be complete before NO undergoes collisional relaxation.