Detection of the transient molecule HOPO in the gas phase by infrared laser spectroscopy

The transient molecule HOPO has been detected in the gas phase for the firs t time using high resolution infrared laser absorption spectroscopy. The mo lecule is formed in the reaction between the products of a microwave discha rge in hydrogen and oxygen, and white phosphorus vapour. Many absorption li nes were detected in the region of the predicted P-O (upsilon(4)) and P=O ( upsilon(2)) stretching modes of cis-HOPO around 850 and 1250 cm(-1) respect ively. About 170 rotational lines of the 850 cm(-1) spectrum have been assi gned to an a-type transition of an asymmetric rotor. The derived rotational constants are compatible with the values for cis-HOPO produced by a densit y functional theory calculation. (C) 2000 Elsevier Science B.V. All rights reserved.