Moment analysis for absorption and magnetic circular dichroism bands of atomicPlarr;Stransitions: Application to matrixhyphen;isolated chromium

摘要

Equations useful for the moment analysis of magnetic circular dichroism (MCD) and absorption bands ofPlarr;Selectronic transitions of atoms or ionsforanyspinmultiplicityhave been derived. In particular, it is shown that the first through third MCD moments, together with the zeroth and second absorption moments may be employed to obtain such electronic and vibronic parameters as (1) the excited state spinndash;orbit coupling constant, (2) the excited state orbitalgfactor, and (3) the contributions of the cubic and noncubic metal/lattice cage modes to the spectral absorption bandwidths. The MCD and absorption spectra of Cr atoms isolated in krypton and xenon matrices are presented. Forbidden transitions between the two allowed7Plarr;7Sbands are observed. Their appearance is ascribed to secondhyphen;order spinndash;orbit coupling to the nearhyphen;lying7Pstates. The moment equations are applied in an appropriate manner to the observed allowed bands. Excited state spinndash;orbit splitting (minus;14 cmminus;1:Cr/Kr and minus;56 cmminus;1:Cr/Xe) are found to be significantly reduced from the gas phase value (+194 cmminus;1) for thez7Plarr;7Stransition. For theythinsp;7Plarr;Sband, an enhancement (+275 cmminus;1:Cr/Kr) and a reduction (+171 cmminus;1:Cr/Xe) from the gas phase value of 206 cmminus;1are observed. It is further shown that the Jahnndash;Teller effect is strongly operative in thezthinsp;7Plarr;7SCr band in both matrices.