Magnetic circular dichroism studies of matrix-isolated atoms: Excited state spin-orbit coupling constant reduction of copper in the noble gases

Abstract

The absorption and magnetic circular dichroism spectra of the 2P+-2S transition of matrixisolated copper atoms have been measured in krypton and xenon matrices. A dramatic reversal in the MCD 'if' term pattern is observed. From a spectral band moment analysis it is shown that: (1) noncubic lattice cage vibrational motions are more important than cubic ones in contributing to the observed bandwidths and (2) the Cu excited state spin-orbit coupling constant (A) in krypton is reduced to 57% of its gas phase value, whereas in xenon it is reduced to -14% of its gas phase value. Calculations using the Moran model show that the excited state geometry of the metal/rare gas cage is distorted via the Jahn-Teller effect in opposite ways in krypton and xenon matrices. The negative sign of A in xenon reveals a reversal in the order of the 2 P state spin-orbit multiplets. Neither this reversal nor the reduction of A in krypton can be accounted for by the Jahn-Teller effect. We attribute the spin-orbit constant reduction to the overlap of the Cu 4p orbital with the np of the rare gas matrix cage atoms. The calculated spin-orbit reduction factors (in Ar, Kr, and Xe) agree well with the experimental ones if a contracted Cu 4p orbital is used. In the same way the ground state g factor shift with matrix atom type, observed by Kasai and McLeod, is semiquantitatively accounted for by calculation of the overlaps between the Cu 4s orbital and the np orbitals of the rare gas cage atoms.

Atomic and molecular defects in solid 4He

“…Due to their large spectral widths, the individual components of the triplet structures strongly overlap and peak positions reported in different publications vary considerably. Triplet structures of the nS → nP transitions have also been observed in absorption spectra of matrix-isolated noble metal atoms [273][274][275][276][277][278]. In those systems usually a single (substitution) trapping site is observed.…”

“…The phenomenon is well known in matrix-isolation spectroscopy as Jahn-Teller effect. As discussed in [282,276,267] the main contribution comes from tetragonal stretching and bending (e g ) modes, and a smaller contribution from trigonal (t 2g ) modes. Calculations of Jahn-Teller spectra were presented for K in solid Ar [265], for Li in Ar, Kr, and Xe [266,285], and for Na in Xe [267].…”

“…Due to the high sensitivity of polarization measurements the dichroism can be measured very precisely and helps to separate overlapping spectral lines. MCD spectra were reported for alkali atoms [266,267] and noble metal atoms [279,[276][277][278] in different rare-gas matrices. A numerical modeling of MCD spectra was recently reported [280,281].…”

Cu 4s → 4p atomic like excitations in the Ne matrix

“…Since the early 1970's the visible, ultraviolet and other spectra of atoms trapped in noble-gas matrices have been reported by many authors. [1][2][3][4][5][6][7][8][9][10][11][12][13][14]16 The Cu atom in a Ne matrix is of interest, because four 12,14 distinct line shapes were observed, not merely three, 11 as set out in Table 1. Three Cu line shapes (known as a triplet 12 ) were also observed in other noble matrices of Ar, Kr, and Xe, [2][3][4][5][6][7][8][9][10] and these are believed to originate from the Cu 4s 1 2 S -4p 1 2 P transition.…”

Metal atom (Zn, Cd and Mg) luminescence in solid neon

“…Several absorption studies [1] of matrix-isolated metal atoms have indicated pronounced threefold splitting on resonance P ← S transitions and while magnetic circular dichroism (MCD) work [2,3] has revealed the origins of the characteristic threefold splitting is likely due to JahnTeller coupling in the excited P state, a fundamental obstacle precluding a conclusive assignment is lack of knowledge of the site occupied by the guest atom in the host solid. Clearly, a better understanding of the underlying physical effects contributing to the spectral behavior of these model matrix-isolated systems relies on an identification of guest site occupancy.…”