Note on the Pt and Hg mass-197 isomers

Abstract

UCRL-11607The decays of Pt 1 9 7 , ptl9?m, Hg 197 and Hgl9?m into the levels of 7~u l9?have been examined with use of semiconductor detector spectrometers. Gamma-ray spectra were recorded with lithium drifted germanium detectors, and internal conversion coefficients were meas.ured with an electron-gamma spectrometer employing both silicon and germanium detectors. The absolute transition probability of the 202 keV E2 radiation connecting the 279 keV (5/2+) and 77 keV (1/2+) states is discussed, within the frame-~ work of the de Shalit model and also.that of Kisslinger and Sorensen.

Further test of internal-conversion theory with a measurement inPt197

“…The survey lists two previous measurements of α K for the 346.5-keV transition in 197 Pt. The first, published in 1965 [20], gave the value α K = 3.9(4), which agrees with our result, albeit with a much larger uncertainty. The second measurement [15] was more recent by 20 years and its result, α K = 4.02 (8), had a much smaller uncertainty, so it was the result that Raman et al chose to adopt for their survey.…”

Decay Studies of 197Tl (2.84 H) and 197mHg (23.8 H)

“…As far «les is concemed, the degree of uncertainty in the experimental values precludes a defmite Statement on a possible E5 admixture. Nevertheless, noting that the theoretical tables [22,23] do not list E5 ICCs, one observes from the Weisskopf nomograms [19], that the partial half-life for the E5 Brought to you by | New York University Bobst Library Technical Services Authenticated Download Date | 6/12/15 11:40 PM 6.2 6.7 [9] transition is 5.0 x 10' ' times in excess of that for the M4 one making the IT transition likely to be of the pure M4 type. The (Tj as well as the N and $ values were taken from our experimental results reported earlier [1].…”

“…Several structural studies [3 -7] have been carried out in the past that have helped to elucidate, among other things, the nature of the negative parity levels below the isomer. However, the determination of the intensities of the transitions from these states and from the isomer is fairly dated [8,9]. The absolute gamma ray intensity of the weak 18.18 keV transition from the 3/2" (152.2) keV level, has not been measured by direct experiment.…”

Level Structure ofAu199from Decay ofPt199

“…The 79th proton in these isotopes moves in the ^3/2 orbit (c^) 3 , and the lowest positiveparity excited states, according to the core-excitation model, may arise from the coupling of the odd nucleon to the 2+ state of the core, leading to the quadruplet 2 + > f + > f + > an d 1 + -Recent measurements 4 in Au 197 have indicated the possibility of such a multiplet and there has been considerable discussion on the nature of the levels in this case. Braunstein and de-Shalit 2 and also de-Shalit 5 have interpreted the low-lying positiveparity levels of Au 197 as mainly due to core excitation.…”