Knowledge Bank

The reaction of laser-ablated vanadium and titanium atoms with methane (or $methane-d4$) under supersonic jet-cooled conditions allows spectra of the methylidynes VCH (VCD) and TiCH (TiCD) to be recorded by laser induced fluorescence. The VCH molecule has been shown to have a $\mathrm{<mrow\; data-mjx-texclass="ORD">3</mrow>}\Delta 1$ ground state and three excited electronic states $(\mathrm{<mrow\; data-mjx-texclass="ORD">3</mrow>}\Delta ,\mathrm{<mrow\; data-mjx-texclass="ORD">3</mrow>}\Phi and\mathrm{<mrow\; data-mjx-texclass="ORD">3</mrow>}\Pi )$ which give rise to bands in the $590-800nm$ $region.1$ Hyperfine-resolved laser induced fluorescence spectra of many of these bands have been assigned with a view to understanding the excited state electron configurations. Following direct pumping from the $0110$ and $0130$ vibronic components of the ground state bending vibration we have determined their separation as $2.6cm-1$. The substitution structure of the ground state is $rs(V-C)=1.7025\backslash AA;rs(C-H)=1.080\backslash AA.$ The TiCH molecule has been found to possess a $\mathrm{<mrow\; data-mjx-texclass="ORD">2</mrow>}\Sigma +$ ground state and several $\mathrm{<mrow\; data-mjx-texclass="ORD">2</mrow>}\Pi$ vibronic excited states which give rise to bands in the $660-730nm$ region. As in VCH the vibrational and rotational structure is heavily perturbed. Fits to high resolution ground state combination differences for TiCH and TiCD have given the substitution structure, $rs(Ti-C)=1.7277\backslash AA;rs(C-H)=1.085\backslash AA.$ Very recently a new band system which may be due to CrCH has been discovered using a chromium target. A comparison of the structures, electron configurations and chemistry of the methylidynes will be presented.