THEORETICAL STUDIES OF DIVALENT VANADIUM IN A MAGNESIUM FLUORIDE HOST
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Date
1987
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Ohio State University
Abstract
Divalent vanadium substituted into weak field fiuoride crystals is an example of a phonon-terminated four-level laser with the emission terminating on vibrationally excited levels of the ground electronic state. Laser action in vanadium-doped magnesium fluoride ($MgF_{2:}V^{+2}$) at a wavelength of $1.12 \mu m (8915cm^{+1}$) was reported by johnson $et al^{1}$ as early as 1966. In an extensive experimental study of the optical properties of $MgF_{2}:V^{+2}$, Moulton $et al^{2}$ discovered an unfavorably strong excited-state-absorption (ESA) transition which overlapped the $^{4}T_{2} \rightarrow ^{4}A_{2}$ laser transition. We have carried out configuration interaction electronic structure calculations on the ground and excited states of $MgF_{2}:V^{+2}$ in order to better understand the nature of the ground and excited state absorption. These theoretical studies represent the most accurate ab initio calculation of the optical spectrum of an ion/host system to date. The calculated position of the zero phonon line corresponding to the origin of the $^{4}T_{2}(B_{2})$ absorption band was found to be in error by only 2.3\%. Similar accuracy was obtained for the peak of the $^{4}A_{2} \rightarrow ^{4}T_{2}$ absorption. As determined from the calculated potential energy curves, the predicted peak of the $^{4}T_{2} \rightarrow ^{4}A_{2}$ emission at $9195 cm^{-1}$ is in error by only $-275 cm^{-1} (3\%)$, which is consistent with the magnitude of the agreement for the zero-phonon line, but opposite in sign. The energies for the ESA transitions from the $^{4}T_{2}(B_{2})$ state to the crystal field split components of the $^{4}T_{1a}$ and $^{4}T_{1b}$ excited states have been calculated and will be discussed.
Description
$^{1}$L.F. Johnson, J.H. Guggenheim, and R.A. Thomas, Phonon Terminated Optical Masers, Phys. Rev. 149, 179(1966), L.F. Johnson and J.H. Guggenheim, Phonon Terminated Coherent Emission from $V^{+2}$ ions in $MgF_{2}$ J. Appt. Phys. 38, 4837 (1967). $_{2}$1981 Laser Program Annual Report, Lawrence Livermore National Laboratory, Livermore, Calif., UCRL-50021-81 (1982), p 7-94; 1982 Laser Program Annual Report, Lawrence Livermore National Laboratory, Livermore, Calit., UCRL-50021-82 (1983).p7-78.
Author Institution: Physics Department, Lawrence Livermore National Laboratory; Department of Chemistry, Ohio State University
Author Institution: Physics Department, Lawrence Livermore National Laboratory; Department of Chemistry, Ohio State University