Orientation of /sup 199m/Hg by optical pumping detected by gamma - radiation anisotropy

/sup 199m/Hg was produced and mass separated at the ISOLDE facility (CERN). Nuclear orientation achieved by optical pumping via the resonance line 6s/sup 2/ /sup 1/S/sub 0/ to 6S6p/sup 3/P/sub 1/, lambda =2537 AA was monitored by means of the anisotropy of the gamma -radiation emitted in the cascade /sup 199m/Hg(I=13/2/sup +/) to /sup 191/Hg(I=5/2/sup -/) to /sup 199/Hg(I=1/2/sup -/). Maximum anisotropies of 35% (2,8%) were found in the M4(E2) transition. A Zeeman scanning of the /sup 3/P/sub 1/ state yielded the positions of F=13/2 and the F=15/2 hfs components relative to the reference isotope /sup 204/Hg at 15.13(15) GHz and -2.86(15) GHz respectively. Isotopic shift and the quadrupole interaction constant were deduced from these values using the known A factor. From the B factor the spectroscopic quadruplment was calculated as Q/sub s/=1.54(44) barn. (30 refs).