Knowledge Bank

Laser-induced fluorescence spectra of jet-cooled HCP$+$ and DCP$+$ have been obtained with the pulsed discharge technique using HCP/DCP and argon precursor mixtures. Most of the excited state vibrational fundamentals have been observed and a set of vibrational constants obtained. High resolution spectra of the $2$\Pi$\mathrm{<mrow\; data-mjx-texclass="ORD">3<mrow\; data-mjx-texclass="ORD">/</mrow>2</mrow>}$ components of the $000$ bands of both isotopomers have been recorded, and these spectra show resolved phosphorus hyperfine structure which allowed the determination of the excited state Fermi contact parameter. The $B$ values were used to obtain the ground and excited state effective geometric parameters as $r0\prime \prime$(CH) = 1.077(2) \AA, $r0\prime \prime$(CP) = 1.6013(3) \AA, $r0\prime$(CH) = 1.082(2) \AA and $r0\prime$(CP) = 1.5331(3) \AA. The ground state vibrational energy levels reported in the literature were fitted to a Renner-Teller hamiltonian that included the effects of angular momentum coupling as well as spin-orbit, vibrational anharmonicity and Fermi resonance effects.