Knowledge Bank

A complicated system of about 30 bands in the 590-800 nm region has been discovered by laser excitation, following the reaction of laser-ablated vanadium atoms with methane under supersonic jet-cooled conditions. At least two electronic transitions must be present, since the most prominent bands are analysed so far have integer rotational quantum numbers, and clear $\mathrm{<mrow\; data-mjx-texclass="ORD">51</mrow>}V$ nuclear hyperfine structure. The presence of hydrogen in the carrier is suggested by experiments with $CD4$. but the simple linear-molecule sub-band structure indicates that the carrier is VCH, rather than $VCH3$. The lower state of the strongest bands in an $\Omega =1$ state, presumably $X3\Delta 1$ by analogy with $VN1$. Wavelength resolved fluorescence experiments reveal a highly structured vibrational level pattern in the ground state, with the most prominent peaks corresponding to levels at 146, 572, 840, 1118 and $1402cm-1$ frequency is probably the V-C stretching vibration, shifted down considerably from its value in the isoelectronic VN molecule. Consistent with this, rotational analysis has given $B\prime \prime =0$. $491cm-1$, which correspond to a V-C bond length of about 1.72 {\AA}, some some 0.15 A longer than in VN while the hypergine h parameter of the ground state $(-0.0083cm-1)$ is less than half that of VN, The 572 and $1118cm-1$ levels seem to involve overtones of the bending vibration, distorted by orbital angular momentum effects, while the $146cm-1$ interval is provisionally assigned as the lowest spin-orbit interval of the ground state. Rotational perturbations are widespread throughout the system. cvcn in the bands near 800 nm. While the A-doubling in the $(\mathrm{<mrow\; data-mjx-texclass="ORD">3</mrow>}\Pi 0$) upper state of the 639 nm band is highly erratic.