A rotation–torsion–vibration treatment with three-dimensional internal coordinate approach and additional FTIR spectral assignments for the CH3-bending fundamentals of methanol

The (0,0) band of the B2(sigma)+–X2(sigma)+ transition of ZrN between 404.1 and 407.1 nm was recorded and rotationally analyzed using laser induced fluorescence (LIF) spectroscopy. Small local rotational perturbations have been found for both spin components. For 90ZrN, perturbations are found at J=23.5 of the F1 component and J=17.5 and 43.5 of the F2 component. The perturbation of the F1 component at J=23.5 shifts to J=18.5 for 94ZrN. Our analysis indicates that these perturbations are caused by more than one electronic state. A least-squares fit of the unperturbed line positions yielded approximated molecular constants for the v=0 level of the B2(sigma)+ state of three isotopic molecules. Ab initio calculations have been performed to obtain spectroscopic properties of the ground and low-lying doublet and quartet states. The agreement between calculated and observed spectroscopic properties of the low-lying doublet states is good.