Difference frequency laser spectroscopy of the ν1 band of the HO2 radical

Abstract

The ν1 (O–H stretching) band of the HO2 radical was observed in absorption by using a difference frequency output obtained from an Ar ion laser and a cw dye laser as a source, combined with a multiple-reflection discharge cell. Zeeman modulation was employed to improve the sensitivity. The HO2 radical was generated directly in the cell by a dc discharge in a mixture of allyl alcohol and oxygen. About 280 lines were observed and analyzed to precisely determine the rotational constants, centrifugal distortion constants, and spin-rotation interaction constants in the ν1=1 state. The band origin was determined to be 3436.1951(4) cm−1, which is 22 cm−1 higher than the value previously obtained by a matrix isolation study.