Submillimeter-wave spectroscopy of phosphaalkynes: HCCCP, NCCP, HCP, and DCP

The submillimeter-wave rotational spectra of the unstable phosphorus-bearin g molecules HCCCP (phosphabutadiyne) and NCCP (C-cyanophosphaethyne) have b een investigated in selected frequency regions between 490 and 815 GHz usin g the Cologne Terahertz Spectrometer. Both molecules were studied in their ground vibrational states. Additionally, vibrational satellites within the bending states v(4) = 1 and v(5) = 1 were recorded for NCCP. Furthermore, t he ground state rotational spectra of the C-13 and N-15 isotopomers of NCCP were detected in natural abundance. The new measurements allowed us to eva luate the sextic centrifugal distortion constants for each isotopomer and v ibrational state investigated. The pyrolysis reactions, through which HCCCP and NCCP were produced in situ, also yielded phosphaethyne, HCP, as a by-p roduct. Some transitions of HCP and DCP were recorded in their ground vibra tional states along with v(2) = 1 vibrational satellites of the former. (C) 2001 Academic Press.