A spectroscopic study of HCP, the phosphorus analogue of hydrocyanic acid

Abstract

The ultraviolet absorption spectrum of HCP has been observed from 4100 Å to about 2350 Å, and seven electronic transitions have been identified. Three of these transitions involve excited singlet states and four of them involve excited triplet states. The symmetries, energies, and equilibrium conformations of these states are listed below:[Formula: see text]Some observations have also been made on the vibration–rotation energy levels of the ground electronic state, [Formula: see text], of HCP. The fundamental vibration frequencies (in cm−1) are ν1 = 3216.9, ν2 = 674.7, and ν3 = 1278.4.

Characterization of singlet ground and low-lying electronic excited states of phosphaethyne and isophosphaethyne

“…4. The possibility exists 6 however, there is reasonable agreement in the vibrational frequencies. The angles differ greatly but the CP bond length exhibits excellent agreement with the experimental values.…”

“…The second singlet excited state ͑B ͒, considered by Johns et al 6 to be a 1 ⌸ state, was reexamined in 1972 by Moehlmann et al 7 in a study exploiting the Zeeman effect. The group found that the Zeeman splitting for the B state increased as the rotational quantum number J increases.…”

“…[3][4][5] The ultraviolet ͑UV͒ spectrum of HCP was first reported in an extensive spectroscopic study by Johns et al in 1969. 6 They deduced ground state information using their own rovibronic analysis along with data from Tyler's earlier microwave study. 2 Fundamental vibrational frequencies for the symmetric and asymmetric stretching and the bending modes were reported as 3217 cm −1 ͑ 1 ͒, 1278 cm −1 ͑ 3 ͒, and 675 cm −1 ͑ 2 ͒, respectively.…”

“…A series of IR studies [10][11][12][13] were conducted that appear to give fundamental stretching vibrational frequencies to greater precision than those reported by Johns et al 6 Kalasinsky and Pechsiri 14 recorded the Raman spectrum in 1985 and determined the fundamental vibrational frequencies, 1 = 3218 cm −1 and 3 = 1277 cm −1 . Mason and Lehman 15 in 1993 measured the laser-induced fluorescence spectrum of HCP and found a sharp decrease in intensity at 41 680 cm −1 .…”

“…Using results obtained for HCN as constraints, Strey and Mills 16 in 1973 used vibration-rotation constants determined by Johns et al 6 to deduce an anharmonic force field for HCP. From this data they determined r e ͑HC͒ = 1.0692͑8͒ Å and r e ͑CP͒ = 1.5398͑2͒ Å.…”