Rotationally resolved spectra of jet-cooled VMo.

The authors report the first gas-phase spectroscopic investigation of diatomic vanadium molybdenum (VMo). The molecules were produced by laser ablation of a VMo alloy disk and cooled in a helium supersonic expansion. The jet-cooled VMo molecules were studied using resonant two-photon ionization spectroscopy. The ground state has been demonstrated to be of (2)Delta(52) symmetry, deriving from the dsigma(2)dpi(4)ddelta(3)ssigma(2) electronic configuration. Rotational analysis has established the ground state bond length and rotational constant as r(0) (")=1.876 57(23) A and B(0) (")=0.142 861(35) cm(-1), respectively, for (51)V(98)Mo (1sigma error limits). Transitions to states with Omega(')=2.5, Omega(')=3.5, and Omega(')=1.5 have been recorded and rotationally analyzed. A band system originating at 15 091 cm(-1) has been found to exhibit a vibrational progression with omega(e) (')=752.7 cm(-1), omega(e) (')x(e) (')=12.8 cm(-1), and r(0) (')=1.90 A for (51)V(98)Mo. The measured bond lengths (r(0)) of V(2), VNb, Nb(2), Cr(2), CrMo, Mo(2), VCr, NbCr, and VMo have been used to derive multiple bonding radii for these elements of r(V)=0.8919 A, r(Nb)=1.0424 A, r(Cr)=0.8440 A, and r(Mo)=0.9725 A. These values reproduce the bond lengths of all nine diatomics to an accuracy of +/-0.012 A or better.