Gas-phase vibrational spectroscopy of the dysprosium monoxide molecule and its cation

Abstract

Rotationally resolved vibrational spectra of DyO and DyO⁺ in a molecular beam are obtained by IR excitation from the X8 ground state and from high-n Rydberg states of DyO using an infrared free electron laser. Vibrational excitation is detected either by resonance enhanced multiphoton ionisation from X8(v = 1) or by autoionisation of Rydberg states converging to DyO⁺(v = 1). For most heavy molecules, the large spectral width of an infrared free electron laser does not allow for rotational resolution. In DyO and DyO⁺ the P, Q, and R transitions can be resolved due to the high angular momentum in their ground states. For ¹⁶⁴DyO a vibrational constant of ω_e = 847.5(2) cm⁻¹ and a vibrational anharmonicity of ω_eχ_e = 2.9(1) cm⁻¹ are deduced. For the ¹⁶¹DyO⁺ cation a transition frequency of ΔG_1/2 = 907(1) cm⁻¹ is found.