Spectroscopy and triplet state lifetime for yttrium fluoride (YF) in inert gas matrices

Abstract

Absorption and emission spectra are reported for YF isolated in Ne, Ar, and Kr matrices and the ground state is confirmed as 1Σ+. Calculated Franck–Condon intensities permit confident assignments of vibrational quantum numbers for most of the states but point to an anomaly in the red emission produced on excitation into the B̃ state. Lifetime studies in argon show that such excitation also depletes ∼90% of the ground state population and that the return requires ∼15 min. As explanation, the ã 3Δ state of YF is proposed as a metastable sink, with the longest lifetime yet reported for a triplet state in matrices. Evidence for direct b̃ 3φ←X̃ 1Σ+ absorption is also presented and this suggests that the ã 3Δ state lies within ∼200 cm−1 of the X̃ state. The lifetime of the ã state is a sensitive probe of coupling of YF to the lattice phonons and it decreases by four orders of magnitude for YF in neon and in a ’’tighter’’ second site in argon.

New electronic transitions in the YF spectrum; energies of thea3Δ andb3Π states

“…The ~ = 1-X 1E band is probably identical to the absorption band at 24 100cm-~ observed for YF isolated in an argon matrix [7]. Now, the only unknown low-lying state is the A IA state.…”

“…The interpretation of the infrared fluorescence spectra of the matrix isolated YF molecule [7] is apparently erroneous. The Kr + line excites a high vibrational level of the baH state rather than a level of the high-lying 3~ state.…”

“…Absorption and laser induced fluorescence spectra have been reported for YF isolated in Ne, Ar and Kr matrices, and the ground state is confirmed as ly. 1,7].…”

“…The value of 3300cm -1 was derived from measurements of the temperature dependence of the relative intensities of the triplet and singiet (B III-X 1Z) systems [8]. The value of 200 cm-1 was proposed on the basis of the interpretation of fluorescence spectrum of the matrix-isolated YF molecule 1,7]. Recent theoretical study of YF 1-9] gave T = 6400-8400 cm-1.…”

Spin-forbidden cΣ1+3←XΣ+1 band system of YF

“…[2][3][4][5][6][7][8][9][10][11] Low temperature matrix isolation studies have been performed 12,13 and theoretical investigations [14][15][16] have confirmed that these molecules exhibit a ground state symmetry of 1 ⌺ + , correlating to the M + ͑ns 2 ͒F − ͑3s 2 3p 6 ͒ ͑M = Sc, Y, or La͒ electronic configuration. High temperature thermal emission and laser spectroscopic investigations on these molecules have revealed several singlet-singlet and triplet-triplet transitions that have been rotationally analyzed, and spectroscopic constants have been determined.…”