ZEEMAN-EFFECT STUDIES OF THE ELECTRONIC ABSORPTION-SPECTRUM OF OCTACHLORODIRHENATE(2-) (RE-RE) IN PULSED 50-TESLA MAGNETIC-FIELDS

Electronic absorption spectra have been measured for crystals of (Bu(4 )N)(2)[Re2Cl8] at 3.8 K in pulsed magnetic fields (pulse duration ca. 10 ms; field strength to 50 T). Spectra were measured in the 530-600 n m ('Band I') and 435-500 nm ('Band II') regions, where well resolved v ibrational fine structure had been noted in previous spectroscopic stu dies. Application of magnetic fields up to 50 T caused no measurable s plittings or shifts in these two absorption bands. This indicates that both bands are attributable to spin-allowed electronic transitions, s ince spin-forbidden transitions would be expected to show Zeeman split ting. Possible assignments for Bands I and II include transitions to t wo (1)E(g) excited states [(1)(pi,delta) and (1)(delta,pi*)], as prev iously suggested by Bursten et al. (B.E. Bursten, EA. Cotton, P.E. Fan wick and G.G. Stanley, J. Am. Chem. Sec., 105 (1983) 3082), and to two formally doubly excited states, (1)A(1g) [(1)(delta delta,deltadelta )] and (1)E(u) [(pi delta,delta*delta*)].