Vibrationally excited states of HC5P: millimetre-wave spectroscopy and coupled cluster calculations

Abstract

A more efficient method for the production of the unstable HC₅P molecule has been found, based on copyrolysis of phosphorus trichloride and cyclopentene. This allowed us to extend the study of the rotational spectrum of HC₅P to a large number of vibrationally excited states which approximately lie between 150 and 650 cm⁻¹, namely (v₆v₇v₈v₉v₁₀v₁₁) = (000002), (000003), (000010), (000020), (000100), (001000), (010000), (100000), (000011), (000101), and (001001). The anharmonic resonances which couple the (100000) stretching state with the (000020) and (000101) bending states, and the l-type resonances which occur between the different sublevels of a given bending state have been taken into account in the analysis of the spectra, which yielded determinations of the α₆, α₇, α₈, α₉, and α₁₀ vibration–rotation coupling constants, and of the x_L(11,11), x_L(10,10), x_L(10,11), x_L(9,11), and x_L(8,11) anharmonicity constants. The experimental work was assisted by coupled-cluster single double triple [CCSD(T)] calculations, performed using the cc-pVQZ basis, which provided accurate predictions for a variety of spectroscopic constants including harmonic vibrational wavenumbers, vibration–rotation coupling constants and l-type doubling constants.