Laser spectroscopy of holmium monosulphide: Electronic, vibrational and rotational structure of the A[14.79]8.5-X8.5, A[14.79]8.5-W[0.25]7.5 and A[14.79]8.5-V[0.98]7.5 transitions

Laser induced fluorescence spectra of HoS have been obtained using a Broida oven and a ring dye laser. Dispersed fluorescence spectra showed transitions from a common upper state, A[14.79]8.5 to the v = 0 and 1 vibrational levels of three low lying states, labelled X8.5, W[0.25]7.5 and V[0.98]7.5 (the states are labelled [10−3T0]Ω according to their energy and Ω assignment). High resolution excitation spectra were obtained for all six transitions and a rotational analysis yielded the following principal constants, in cm−1, for the X, W and V states, respectively: T0 = 0, 251.8713(31), 980.6969(37); Be = 0.121903(42), 0.121729(37), 0.122561(34); ΔG1/2 = 463.8811(46), 462.9411(45), 461.2084(127). For the A state, T0 = 14794.6987(28) cm−1 and B0 = 0.112596(29) cm−1. The three low lying states are shown to arise from the Ho2+[4f10(5I8)6s]S2− configuration in accord with Ligand Field Theory predictions. The atomic origin of each of the three low lying electronic states was determined from the observed resolved hyperfine structure.