摘要
Time‐resolved Fourier‐transform spectroscopy and two‐color laser‐induced grating spectroscopy are two new techniques recently employed in this laboratory. We recorded emission in the near infrared region during laser photolysis of HONO 2 with a step‐scan Fourier‐transform spectrometer and achieved temporal resolution in the microsecond range and spectral resolution of 0.1 cm 1 . Rotationally resolved emission lines of the (0,0) band of the D 2 ∑ + →A 2 ∑ + transition of NO in the region 8900‐9300 cnv −1 with irregular relative intensities were observed when an ArF excimer laser was used to photodissociate HONO 2 . The spectroscopic parameters of both D 2 ∑ + and A 2 ∑ + states agree with those previously reported. When a narrow‐band ArF laser was used, selective rotational levels of the D state of NO were populated depending on the wavelength of the ArF laser. Our results indicate that absorption of a 193‐nm photon by NO(υ″ = 1) is responsible for the observed emission. To test the technique of two‐color laser‐induced grating spectroscopy, we employed the B 3 II 0U + ‐X 1 ∑ g + system of I 2 . Background‐free spectra with transitions involving rotationally selected states were recorded. Various experimental schemes were employed with population gratings formed in either the B or X state. Signals due to different four‐wave mixing schemes were distinguished by variation of relative timing between the grating beams and the probe beam. Copyright © 1995 The Chemical Society Located in Taipei & Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim, Germany