Electric quadrupole moments of radioactive Pt isotopes

Nuclear orientation experiments were performed on¹⁸⁹Pt (I=3/2^–; T_1/2=11 h),¹⁹¹pt (I=3/2^–; T_1/2=2.8 d) and^195mpt=3/2^–; T_1/2=4.0 d) in an Os single crystal at temperatures down to 10 mK. Preliminary results for the quadrupole splitting _o=e²qQ/h are +48 (9), +39 (6), and –87 (12) MHz for¹⁸⁹ptOs,¹⁹¹ptOs, and¹⁹⁵mptOs, respectively. Preliminary results for the quadrupole moments are –0.8 (4), –0.6 (3), and +1.4 (7) b for¹⁸⁹pt,¹⁹¹pt, and¹⁹⁵mpt, respectively. In addition, the quadrupole subresonance structure of¹⁸⁹pt and¹⁹¹pt in Fe was measured with quadrupole-interaction resolved NMR-ON spectroscopy. The results for the magnetic hyperfine splitting _M=¦g_NB_HF/h¦ and _Q are:¹⁸⁹ptFe: _M=277.9 (1) MHz; _Q=+1.39 (5) MHz.¹⁹¹ptFe: _M=320.17 (3) MHZ; _Q=+1.39 (3) MHz. The ratio of the quadrupole moments of¹⁹¹pt and¹⁸⁹pt is deduced to be Q (¹⁹¹Pt/Q^l89pt)=+1.00 (4). The negative quadrupole moments of¹⁸⁹pt and¹⁹¹pt indicate a predominantly oblate shape of the ground states.