The half-lives of nine isomeric states in the rare earth region were measured using magnetic beta-ray spectrometers and an associated fast-slow coincidence system utilizing a time-to-pulse-height converter. The half-lives of the 8. 40-, 118and 139-keV levels in Tm1 69 were determined to be (4. 13 ± 0. 12) nsec, (63 ± 7) psec and (289 ± 24) psec, respectively. The half-life of the 8. 40-keV level was determined using both Erl69 and Ybl69 decay. Several different methods were used to measure the 8. 40-keV level lifetime including applying various accelerating voltages to the radioactive sources. Comparisons are made with theory for the K = 1/2 rotational band in Tm169. The half-life obtained for the 8. 40-keV level in Tm169 corresponds to an energy level width of (1. 10 ± 0. 03) x l0-7 eV. If there were no broadening of the individual line profiles in the Mossbauer effect pattern, the width at half-maximum of the resolved Mossbauer lines would be (2. 20 ± 0. 06) x 10-7 eV compared to the narrowest experimental Mossbauer gross line width of 5. 04 x 10-7 eV. The half-lives of the 87and 105-keV levels in Gd155 were also determined and were found to be (6. 27 ± 0. 35) nsec and (1. 20 ± 0. 04) nsec, respectively. Comparisons were made with the theoretical predictions of Nilsson for these two levels. The theoretical-experimental comparison would assign a spin of 5/2 to the 1 05-keV level and a spin of 3/2 to the 87-keV level if the comparison could be taken at face value. The half-lives of the 122-keV level in Sml52, 89-keV level in Gdl56, 396-keV level in Lu175 and 80-keV level in Prl44 were also determined. The half-lives of these four levels were found to be (1. 36 ± 0. 06) nsec, (2. 22 ± 0. 08) nsec, (3. 31 ± 0. 10) nsec and (143 ± 11) psec, respectively. These four half-life values agree well with values obtained by other investigators.
[1]
C. Coulter,et al.
THE MOSSBAUER EFFECT.
,
1966
.
[2]
J. M. Poindexter.
Electronic shielding by closed shells in thulium compounds
,
1964
.
[3]
E. Hatch,et al.
A COMPUTER METHOD FOR DETERMINING BY LEAST SQUARES GAMMA RAY RELATIVE INTENSITIES USING A BENT-CRYSTAL MONOCHROMATOR
,
1964
.
[4]
J. Styczeń,et al.
MAGNETIC INTERACTION OF THE $sup 155$Gd NUCLEUS IN THE 87-kev EXCITED STATE WITH THE ELECTRONIC SHELL
,
1963
.
[5]
K. Runge,et al.
Measurements of E1 transition probabilities in several deformed odd-mass nuclei as a study of single particle motion
,
1961
.
[6]
P. H. Heckmann,et al.
NUCLEAR ISOMERISM IN In
,
1961
.
[7]
I. Perlman,et al.
Theoretical nuclear physics
,
1953
.
[8]
J. B. French,et al.
THEORY OF MULTIPOLE RADIATION
,
1953
.
[9]
M. Fierz.
On the theory of multipole radiation
,
1949
.