Laser spectroscopy of the à 2Π←X̃ 2Σ+ transition of ytterbium monoacetylide

Abstract

The first spectroscopic identification and characterization of ytterbium monoacetylide (YbCCH) is reported. By combining resonance-enhanced two photon ionization (R2PI), laser-induced fluorescence (LIF), and photoionization efficiency spectroscopy (PIE) with density functional calculations the X̃ 2Σ+ and the à 2Π1/2,3/2 states of YbCCH as well as the X̃ 1Σ+ state of YbCCH+ have been characterized. The à 2Π1/2,3/2–X̃ 2Σ+ system whose 0-0 band for the à 2Π1/2 component lies at around 16 848 cm−1 for YbCCH has been studied at 0.3 cm−1 resolution. The excitation spectra, both R2PI and LIF are characterized by progressions involving the YbCC bending mode (ν5) whose wave number has been determined to be 96 and 103 cm−1 for the X̃ 2Σ+ and à 2Π1/2,3/2 state, respectively. The dispersed fluorescence spectra show a progression in the Yb-C stretching vibration with a wave number of ω(ν3)=328 cm−1. Density functional calculations confirmed the vibrational assignment and yielded a linear geometry for both the X̃ and à state of YbCCH as well as for the X̃ 1Σ+ state of the cation. Photoionization efficiency spectroscopy yielded an adiabatic ionization potential of 47 165(10) cm−1 [5.8477(12) eV]. Rydberg series converging to the 51 and 52 level of YbCCH+ were observed and combined with the appearance potentials led to ω(ν5)=97 cm−1 for the YbCC bending mode of YbCCH+.