DETECTION OF SHORT-LIVED PH2I BY HIGH-RESOLUTION INFRARED AND MILLIMETER-WAVE SPECTROSCOPY - THE GROUND, V(3), V(4), AND V(6) EXCITED-STATES

By low-resolution IR spectroscopy the nu(2) and nu(3) fundamental vibr ations of the hitherto unknown PH2I molecule were detected when P2H4 w as reacted with HI in the gas phase. At room temperature and a pressur e of 1-4 mbar the half-life of PH2I was determined to be ca. 30 sec. H igh-resolution IR spectra (resolution ca. 6 X 10(-3) cm(-1)) were reco rded in the nu(3) and nu(6) regions near 750 and 340 cm(-1). While rot ational J, K lines of the near symmetric top molecule were resolved in the nu(3) band, the nu(4) band revealed sharp (although unresolved) J clusters, which were also found for the hot bands 2 nu(4)-nu(4) and 3 nu(4)-2 nu(4). Millimeter-wave spectra were recorded in the 350 to 46 0 GHz range, and ground state constants determined by merging Delta K- a = 0 pure rotational data with ground state combination differences. For Lambda reduction and I' representation the following constants wer e determined: A = B(z)4.35(5), B = B(x)0.104 876(3), and C = B(y)0.104 646(3) cm(-1). The analysis of the nu(3) band revealed a c-type Corio lis resonance of nu(3), nu(0), 752.525 25(7) cm(-1), with nu(6), nu(0) 742.684(11) cm(-1), and zeta(3,6)(c) (-)0.094 2(1). The nu(4) level, nu = 337.604 14(5) cm(-1), and its overtones n nu(4), n = 2 and 3, are apparently unperturbed. Very good consistency was found with ab initi o predicted molecular parameters, of which several were adopted in our fits when experimental data were not available. (C) 1995 Academic Pre ss, Inc.