keV Cascade Research Articles

Directional correlation of gamma rays in Sn 117

The gamma-gamma directional correlation function for the 560 keV–160 keV cascade in Sn 117 has been measured. The experimental expansion coefficients were found to be A 2=−0.043±0.006 and A 4=0. A unique spin assignment of 7 2 , 3 2 , 1 2 has been made for the 720 keV, 160 keV levels and ground state, respectively. The 560 keV transition is pure E2 while the 160 keV transition is M1+E2 with an E2 content of 1.2±0.5%. The experimental data are compared with theoretical predictions.

The decay of Cd 117 and Cd 117m and directional correlation of gamma rays in In 117

The gamma rays of In 117, following the beta decay of Cd 117 and Cd 117m were studied with a scintillation coincidence spectrometer. The prominent energy levels are 310, 400, 590, 745, 860, 1070, 1710, 1880, 1975, 2120 and 2320 keV. The directional correlation functions for the 345 keV-90 keV and 1290 keV-280 keV cascades in In 117 have been measured. A spin of 3 2 has been assigned to the 400 keV and 590 keV levels. Possible spins for the 745 keV level are 1 2 , 3 2 , 5 2 and for the 1880 keV level the spins may be 1 2 or 3 2 . The experimental level structure is compared with the theoretical predictions.

Directional correlation of gamma rays in Rh 105

Gamma-gamma coincidence measurements on the decay of 4.4 h Ru 105 to Rh 105 form the basis for the decay scheme proposed. Directional correlation measurements have been made on the 315–470 keV, 485–470 keV and the 317–148 keV cascades. The respective correlation functions are: W = 1−(0.012)±0.010)P 2( cos θ) , W = 1+(0.079±0.019)P 2( cos θ)+(0.031)±0.022)P 4( cos θ) , W = 1+(0.161±0.020)P 2 cos θ)−(0.036±0.023)P 4( cos θ) . Spin assignments consistent with these measurements have been made to the levels involved.

Measurement of the internal conversion coefficient ratios by a sum coincidence technique using a solid state detector

A recently proposed sum coincidence technique, for the direct measurement of the ratios of internal conversion coefficients of cascade transitions, has been shown to yield values for these ratios which are in excellent agreement with those obtained by other methods. This new method is independent of the relative intensities of the cascade transitions and of the half life of the parent isotope. Cascade transitions in the levels of As 75 and Cs 131 have been studied. The ratios of the total internal conversion coefficients for cascades from the 401 keV level in As 75 have been found to be: α 121 α 280 = 5.5±0.6; α 136 α 265 = 4.0±0.3 . The value obtained for the ratio of the K conversion coefficients of the 124 keV-496 keV cascade in Cs 131 was 65±5. Measurements on the K (L+M) ratios for the 124, 216, 373 and 496 keV transitions in Cs 131 yielded the following values: ( K (L+M) ) 124 = 2.6±0.2, ( K (L+M) ) 216 = 3.1±0.3 , ( K (L+M) ) 373 = 4.6±0.5, ( K (L+M) ) 496 = 6.1±0.5 .

Energy levels of Pm 149

The gamma rays of Pm 149 following the beta decay of Nd 149 have been studied using fast-slow coincidence techniques. A total of 18 gamma rays have been identified. Levels are established in Pm 149 at 114, 188, 210, 265, 386, 535, 650 and 750 keV. The gamma-gamma directional correlation of the 270 keV-265 keV cascade has been measured and the expansion coefficients have been found to be A 2 = −0.22±0.01 and A 4 = 0. The energy levels found in this investigation are discussed in terms of recent nuclear models.

Delayed angular correlation in liquid sources

Delayed gamma-gamma angular correlations were measured for the 173–247 keV cascade in 111Cd from sources of 111In dissolved in hydrochloric acid, glycerine and acetic acid. The measured attenuation of the coefficients of the angular correlation function is discussed in terms of the interaction mechanism which produces these attenuations.

Der Zerfall des 4,4 min-Rh104m

The decay of the 4.4 min-Rh104m has been investigated by observing coincidences between conversion electrons and gamma quanta. The decay by a 77 keV−52 keV cascade has been confirmed. In addition, a highly converted (31±2) keV transition in coincidence with the known 97 keV gamma ray has been found. The multipole order of this transition has been determined asM3. The intensity of the 97 keV−31 keV cascade has been measured as 3.3 % of the intensity of the 77 keV−52 keV cascade. An indication of a 45 keV transition from the 97 keV level to the 52 keV level has been found with an intensity of at most 0.1 % of the intensity of the 77 keV−52 keV cascade.

The electromagnetic properties of Tm 169

The rotations of the angular correlation of the 198-118 keV and of the 177-130 keV cascades observed in the decay of Yb 169 into Tm 169 have been measured in an external magnetic field. A source of YbCl 3, dissolved in water was used. With a paramagnetic correction factor of 5.31 for the enhancement of the magnetic field at the nuclear site, and the experimental values for the lifetimes of the 5 2 and 7 2 rotational states in Tm 169, the magnetic moments μ 5 2 = 0.61±0.12 n.m. and μ 7 2 = 1.31±0.18 n.m. have been derived. An analysis of all experimentally known electromagnetic properties of the ground state rotational band in Tm 169 is presented and it is found that fifteen measured electromagnetic quantities can be represented by one set of the four rotational parameters Q 0, g K, g R and b 0 .

Observation of dipole-octupole mixture in the gamma-decay of the 1174 keV isomeric state of Yb 172 and its magnetic moment

Measurements of γγ-angular correlations in the decay of Lu 172 revealed that the 1095 keV γ-transition has the unusual multipole mixture of 95% dipole radiation with 5% octupole radiation. This transition is strongly retarded by the K selection rule. We redetermined the half life of the 1174 keV state as T 1 2 = 8.4±0.3 ns . The g factor of the state has been measured by applying the spin rotation method. The result g = +0.214±0.014 was compared with the predictions of the Nilsson model. The best fit was obtained for the two-neutron configuration [514↓–521↓]. The g factor measurement as well as additional γγ-angular correlation measurements favour the assignment of a positive parity to the isomeric state. Angular correlation measurements of the 901 keV-1095 keV cascade and the 811 keV-91 keV-1095 keV triple cascade agree with the assignment of the spin I = 4 to the 2075 keV state; only the spin I = 2 cannot be excluded. The angular correlations are slightly attenuated by interactions with the strong fields of the unfilled 4f electronic shell. We derived the spin relaxation time of the 4f shell as τ J = (2.0±0.5) · 10 −13s. This result was obtained for liquid sourced of LuCl 3 solved in dilute hydrochloric acid.

The Decay of Ba131 and Excited Levels in Cs131

The decay of Ba 131 was studied with a magnetic beta spectrometer and Nal scintillation spectrometers. Twenty-two transitions in Cs 131 were observed in the internal conversion spectrum. A new level in Cs 131 was found at 594 keV. The gamma-gamma angular correlation for the 924-124 keV cascade in Cs 131 was observed to be W(θ)=1+(0.0012±0.016) P 2 (cos θ)+(0.011±0.029) P 4 (cos θ). The spins and parities of excited states of Cs 131 are assigned from the multipolarities which were determined by the internal conversion and the angular correlation. The observed energy levels (in keV) and the spins and parities in Cs 131 are 77(7/2 + , 3/2 + , 5/2 + ), 124(3/2 + , 1/2 + , 5/2 + ), 133(3/2 + , 7/2 + , 5/2 + ), 216(3/2 + ), 374(3/2 + ), 594(?), 620(1/2 + , 3/2 + ), 700(?), 1051 keV (3/2 + , (1/2 + )).

Decay of Tc 96

The multipolarities of the different γ-rays of Mo 96 following the decay of the 4.3 d Tc 96 were measured from the internal conversion coefficients using the Siegbahn-Slätis β-ray spectrometer. The 317.2 keV and 1115 keV γ-rays have been found to be of M1 and E2 characters, respectively. The γ-γ angular correlation measurements were made employing the summing technique of Hoogenboom for the 317–1115 and 1115—841 keV cascades.

A re-investigation of the decay of Eu 147 to Sm 147

A re-investigation of the decay of Eu 147 has been undertaken; gamma-ray intensity measurements and gamma-gamma directional correlations have been performed using an isotopically and chemically pure source. Gamma-gamma directional correlations were measured for the 680-122 and 957-122 keV cascades; the data were consistent with the predominantly M1 assignment for the 680 keV transition based on internal conversion data. Evidence has been found for seven new gamma-ray transitions with energies of 1122, 1195, 1250, 1320, 1326, 1423 and 1448 keV. Gamma-gamma coincidence measurements performed on a chemically but not isotopically pure source of Eu 147 showed that the 1122 and 1250 keV transitions are in coincidence with the 198 keV transition and that the 1195, 1326 and 1423 keV transitions are in coincidence with the 122 keV transition. The energy of the previously reported 881 keV transition was measured and found to be 862 keV. This transition is shown to proceed from a level of 1060 keV; internal conversion coefficient data and gamma-gamma directional correlations indicate that the spin and parity of this level would be 3 2 + assuming a spin sequence for the three lowest levels of 7 2 −, 5 2 − and 3 2 − . The total positon feeding was determined to be (0.54±0.08)% of the total decay. The experimental results are compared with the theoretical results obtained by Schima employing quasi-particle states to account for the short-range forces and zero, one and two phonon states for the collective effects.

The measurement of the L shell particle parameters in the 42 keV E3 transition of Ir 191

The 42 keV-129 keV cascade in Ir 191 has been studied with a single-gap electron-gamma angular correlation spectrometer. The ratio of the K conversion electron to L conversion electron intensity of the 129 keV transition is K/ L = 4.42 while the L subshell ratio is (L I+L II/L III = 7.55±0.35 resulting in the magnitude of the mixing amplitude of the 129 keV transition being | δ| 129 = 0.40 or | δ| 129 = 0.395±0.015, respectively. In the 42 keV transition the L subshell ratio is (L I+L II)/L III = 0.97±0.03 indicating the transition to be a pure E3. Directional correlations with the 42 keV L shell electrons and the 129 keV gamma ray were measured and are of the form W( θ) = 1 + A 2 P 2(cos θ). The results with metallic Os sources on different metallic backings are similar. The average values are A 2(42 L II e −−129 γ) = −0.305±0.012 , A 2(42 L III e −−129 γ) = −0.313±0.013 , for the L II and L III e −-γ correlations, respectively. From these correlations and the theoretical form of the particle parameters it is shown that δ 129 is negative. From the e −-γ correlations and the L subshell ratios, the E3 particle parameters that enter the A 2 term for the L II and L III electrons are b 2(42 L II ) = 0.965±0.040 , b 2(42 L III ) = 0.991±0.043 . Numerical theoretical values for L shell particle parameters have not yet been calculated.

The 26.8 keV state of I 129

The half-life of the 26.8 keV level of I 129 has been measured and found to be 14.4±0.5 nsec. The angular correlation of the 450 keV-26.8 keV cascade of I 129 was found to be isotropic to within 2%.

Decay of 5.4 d Pm 148

The spin and parity of the 1.46 MeV excited state of Sm 148 populated by the decay of 5.4 d Pm 148 have been investigated using angular correlation techniques. Both directional correlation and polarization direction correlation measurements have been made on the 910–550 keV cascade. On the basis of these measurements, it has been possible to make an assignment of 1 − for the spin and parity of the 1.46 MeV level.

Measurement of the g-factor of the 412 keV state in Hg 198

The precession in the internal field of the angular correlation pattern of the 675 kev--412 kev cascade of Hg/sup 198/ following BETA -decay of Au/sup 198/ was measured to determine the g-factor of the 412-kev state. g was found to be +0.38 plus or minus 0.68. (R.E.U.)

Messung der γ-γ richtungskorrelation der 426-404 keV kaskade des Pb 211 Zerfalls

The γ-γ directional correlation of the 426-404 keV cascade in the decay of Pb 211 was studied with a coincidence scintillation spectrometer. Measurements were performed with a liquid and a solid source. The observed coefficients of the correlation function are as follows: liquid source: A 2= −0.105±0.008; A 4= −0.005±0.013 , solid source: A 2= −0.081±0.009; A 4= −0.003±0.013 . Since the measured conversion coefficients allow M1 and E2 mixtures in both transitions it was not possible to make a unique assignment.

Experimental evidence of an error in the conversion electron-gamma correlation theory: Level spins in I 127

The spins of states in I/sup 127/ populated by the K-capture decay of Xe/ sup 127/ were determined. The relative conversion line intensities of the I/sup 127/ transitions and the gamma-gamma, conversion electron-gamma, and gamma- conversion electron angular correlations for the 172.1--202.8 kev cascade were measured. (R.E.U.)

Gamma-gamma angular correlations in Re 187

Angular correlation measurements have been made on the 72 keV–134 keV and 552 keV– 134 keV gamma-ray cascades in Re 187 following the decay of 24 h W 187. The observed correlation functions are W( θ) = (1±0.004)−(0.047±0.024) P 2(cos θ)+(0.004±0.041) P 4(cos θ) and W( θ) = (1±0.006)−(0.034±0.017) P 2(cos θ)−(0.007±0.030) P 4(cos θ), respectively, for the two cascades. The results are consistent with the spin values 9 2 and 5 2 for the excited energy levels at 206 keV and 686 keV, respectively. The above correlation functions are considerably different from those reported by Behrend and Neuert 1) for the 72 keV–134 keV cascade and by Arns and Wiedenbeck 2) for the 552 keV–134 keV cascade.

Investigation of the decay scheme of Cr 51

The energy distribution of γ-rays arising from the decay of Cr 51 was investigated by the scintillation method. Besides the well-known, most intense transition of 323 keV, we also found the 323 keV and 320 keV cascade transitions of low intensity. At 150 keV a new γ-transition in cascade with the line of 323 keV was found. A cross-over transition of 470 keV energy was observed in parallel with the cascade.