The absorption and MCD spectra of the2Pthinsp;larr;thinsp;2Stransition of Cu atoms isolated in argon matrices have been measured over the temperature range 13ndash;25 K. Spectral band moments (up to third order in MCD) have been determined and parameters of interest extracted from them. The observed triplet bandsrsquo; separation and MCDCterm signs are analyzed assuming a static trigonal site distortion. It is shown that a static site distortion model is incapable of reproducing the experimental results. Simultaneous spin orbit and noncubic lattice vibrational couplings (Jahnndash;Teller effect) are shown to be active in the Cu excited2Pstate. The observed triplet of bands and its MCDCterms are satisfactorily described by an adiabatic model developed by Moran. Comparison of the observed band shape to ones calculated by Cho using Monte Carlo methods show that simultaneous spinhyphen;orbit andeandt2lattice mode interactions are operative. The observed reduction of 25percnt; in the excited state spinhyphen;orbit coupling constant is attributed to the overlap of Cu 4porbitals with the Ar 3porbitals. A new method for the determination of the temperature of matrixhyphen;isolated samples is described. The temperature dependence of the MCD first moment and absorption zeroth moment of a matrixhyphen;isolated paramagnetic species is determined once to find the lowest temperature attainable.
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