keV Cascade Research Articles

The g-factor measurement of the 206 keV [formula omitted] state of 187Re

The nuclear g-factor of the 206 keV 9 − 2 state (T 1 2 = 0.55 μs) in 187Re, has been measured using the differential angular correlation method and a magnetic field of about 3100 ± 30 G. The g-factor of this state comes out to be g = 1.04 ± 0.04. The angular correlation measurements on the 72–134 keV and 552−134 keV cascades were also performed.

The magnetic moment of the lowest 3/2− state in57Co

The reaction54Fe(α, n)57Ni has been used to implant57Co isotopes in ferromagnetic iron. Theg-factor of the lowest 3/2− state is determined using the internal field in a constant angle reversed field method. The angular correlation of the 127–1,378 keV cascade is also measured. The result of the angular correlation measurement together with reaction data is consistent withp3/2 andp1/2 single particle assignments to the lowest 3/2− resp. 1/2− state. In view of this statement the quenching of the magnetic moment is discussed.

Magnetic moment of a suggested three-quasiparticle state in 125Te

The magnetic moments of the 321 keV 92− and 464 keV 52+ levels of 125Te have been determined by the PAC method to be μ = −(0.918 ± 0.032) n.m., and μ = −(0.58 ± 0.27)n.m., respectively. The result for the 321 keV level agrees with the prediction of Kisslinger's three-quasiparticle model. The values of the angular correlation coefficients of the 321–177 keV and 204–177 keV cascades are, after correction for background coincidences and solid angle, A2 = −0.168 ± 0.012, A4 = −0.003 ± 0.015 and A2 = −0.403 ± 0.014, A4 = + 0.003 ± 0.020 respectively. The mixing ratio for the 204 keV (72− − 92−) transition is δ(E2/M1) = −1.88 ± 0.22 giving an E2 content of Q(E2) = 0.78 ± 0.04, while for the 321 keV (72+−92−) transition 0 ≦ Q(M2) ≦ 0.010 and −0.22 ≦ δ(M2/E1) ≦ 0. The magnetic hyperfine field for tellurium in gadolinium has been measured with the result Bhf = −38 ± 10 kG. The electric quadrupole interaction frequency of the 321 keV level for Te in Gd is ωOE = (270 ± 70)·106 rad/s.

Directional correlations of gamma rays in 152Sm and 152Gd measured by means of two Ge(Li) counters

Directional correlation measurements have been performed with two Ge(Li) counters on several γ rays in coincidence with the 121.78 and 334.31 keV γ transitions which de-excite the first 2+ levels in 152Sm and 152Gd, respectively. A total of 20 γ−γ directional correlations, 13 in the 152Sm nucleus and 7 in the 152Gd nucleus, was measured simultaneously. Several of the γ−γ directional correlations involved gamma transitions of weak intensity, for example the (688.66−121.78), (1457.4−121.78), and (1528.16−121.78) keV cascades in 152Sm and the (586.29−334.31) and (1089.73−334.31) keV cascades in 152Gd. Among the various results which could be extracted from these measurements, the most interesting appears to be the determination of a nearly pure E2 character for the 688.66, 964.01, 1112.04, and 867.33 keV gamma transitions. The first two γ rays de-excite the 2+ β- and γ-vibrational levels to the 2+ ground-state rotational level at 121.78 keV in 152Sm, whereas the last two γ rays de-excite the3+ γ-vibrational level to the 2+ and 4+ (at 366.44 keV) ground-state rotational levels in 152Sm.

The Decay of 103Ru

The gamma rays in the decay of 103 Ru to 103 Rh have been investigated with scintillation spectrometers in fast-slow coincidence, sum-coincidence and sum-peak coincidence modes. In the literature there is a lot of ambiguity about the existence of 65, 112, 176, 322 and 362 keV gamma transitions. Present measurements confirm the existence of these transitions. A 362 keV gamma transition between the 362 keV level and the ground state of 103 Rh has been found to have an intensity \({\leqslant}0.01\)%. Directional correlations of the 445-53 and 557-53 keV cascades have been observed and indicate spin-parity assignments 9/2 + , 7/2 - and 9/2 - for the 93, 538 and 650 keV levels of 103 Rh.

Electric Quadrupole Field in `HfOCl2·8H2O' Crystals

The perturbed angular correlation of 133-482 keV cascade in Ta 181 has been measured with the source in the form of HfOCl 2 ·8H 2 O crystals with magnetic fields up to 20 kG. The experimental values of G 2 and G 4 , when compared with the theoretical values of Abragam and Pound, give the quadrupole interaction frequency ω E 0 =(118±20) Mc/s. The experimental values obtained under the presence of external magnetic field show the effect of time dependent fields present in this crystal.

Investigation of statistically perturbed angular correlations of154Gd and156Gd in different liquid sources

The statistical perturbations of γγ-angular correlations involving the first 2+ rotational state of154Gd and156Gd have been time differentially investigated. We used liquid sources of 3+ ions of Gadolinium in lN perchloric acid, 0.5 N and 1N hydrochloric acid, 1.3N and 2.6 N sulfuric acid. Influences of the various chemical surroundings on the ratio λ4/λ2 of the attenuation parameters have been found. A simultaneous measurement of the angular correlation of the 874 keV–123 keV cascade and the 2,098 keV–89 keV cascade of154Gd and156Gd, respectively, has been performed in perchloric solution. From the ratio of the attenuation parameters λ2, obtained by this experiment, we have derived the ratio of the magneticg-factors of the first 2+ levels of these isotopes asg 154/g 156=1.11±0.08.

Directional correlation studies in the decay of177gLu

Directional gamma-gamma correlations of the strong 208.4–112.9 keV and of the weak 71.6–249.7 keV cascade transitions in the decay of177gLu have been measured. The correlation coefficientsA22=−0.208±0.012 of the strong andA22=−0.105±0.005 of the weak cascade have been determined. The mixing ratioE2/M1 of −3.7±0.3 for the 112.9 keV transition and theM2/E1 of −0.0173±0.0065 for the 71.6 keV transition have been obtained. The deducedM2 admixture in the 71.6 keV transition is in good agreement with the theoretical estimates of Weisskopf and of Nilsson.

The 521 keV Beta transition in182Ta decay

The beta-gamma directional correlation of the 521-67 keV cascade in182Ta decay was measured to investigate the higher-order effects. The observed correlation function at $$\bar E_\beta = 450 keV$$ is found to be isotropic and is given byW β−γ(ϑ) (at $$\bar E_\beta = 450 keV$$ )=1+(0.025±±0.031)P 2(cosϑ). TheA 22 coefficient indicates no higher-order contributions to the 521 keV allowed but hindered beta transition of182Ta.

Angular correlation of the 460 keV-27.7 keV gamma-gamma cascade in 129I

Normalized expansion coefficients A 22 = −0.0148 ± 0.0029 and A 44 = −0.0068 ± 0.0043 have been found for the angular correlation of the 460 keV–27.7 keV cascade in 129I, in contradiction with some earlier measurements. These results are consistent with a spin 3 2 or 5 2 assignment of the 487 keV level. For both spins the E2 M1 mixing ratio of the 460 keV transition is given. Unfortunately, no conclusion can be drawn about the sign of the mixing ratio of the 27.7 keV transition.

Time differential angular correlation measurements on 160Dy and the electric quadrupole moment of the first excited state

The statistical perturbation of the angular correlations of the 1178 keV-87 keV cascade and the 879 keV-87 keV cascade of 160Dy has been investigated by time differential measurements. We used liquid sources of 3 + ions of 160Tb in 1 N perchloric acid, 1 N sulphuric acid, and 0.01, 1.0, 3.0 and 10.0 N hydrochloric acid. In all cases the measured angular correlation coefficients A 2 and A 4 are well described by single exponential functions. The results for the attenuation parameters λ 2 and λ 4 for the perchloric solution and the solution in sulphuric acid are: λ 2 = (0.0686 ± 0.0054) · 10 9 sec −1 λ 4 = (0.2118 ± 0.0186) · 10 9 sec −1 sulphuric acid, λ 2 = (0.0687 ± 0.0074) · 10 9 sec −1 λ 4 = (0.2102 ± 0.0193) · 10 9 sec −1 perchloric acid, respectively. The values of hydrochloric acid observed for different normalities agree within the limits of error. The weighted average is: λ 2 = (0.0804 ± 0.0030) · 10 9 sec −1 λ 4 = (0.2452 ± 0.0082) · 10 9 sec −1. We observed no indication of an influence of the chemical structure on the ratio of λ 4/ λ 2. The average of all measurements is λ 4/ λ 2 = 2.10 ± 0.15 (4.9 %). From this ratio we derive for the electric quadrupole-moment of the first excited state the value (1 − R) Q sp, = 1.67 ± 0.46 b. This result is in agreement with Coulomb excitation data.

The radioactive decays of 6.7 min 179mW and 38 min 179W

The decays of 6.7 min 179mW and 38 min 179W have been studied by means of high resolution γ-ray and electron spectroscopy using Ge(Li) and Si(Li) detectors, a broad-range transport solenoid electron spectrometer and γ-γ coincidences with Ge(Li) detectors. The decay of 38 min 179W occurs by a fast beta transition (log ft 4.6) and by a first-forbidden beta transition (log ft 6.9) followed by a 30.7 keV and by a 133.9 keV γ-transition, respectively. The [521] 1 2 − 6.7 min 179mW decays mainly by an isomeric transition of 221.5 keV (M3) and a competing 101.6 keV (E4)-120.1 (E2) keV cascade to the 179W ground state. A small fraction of the decay of the 6.7 min isomer is observed to proceed by beta transitions to levels in 179Ta. The results are interpreted in terms of the Nilsson model and the following intrinsic proton states are proposed in 179Ta: [404]if 7 2 + giound state; [514]if 9 2 − 30.67 keV; [402]if 5 2 + 238.7 keV; [411]if 1 2 + 520.4 keV; and [541]if 5 2 − , K = 1 2 at 741.5 keV. The [541] if 1 2 − band is observed to have approximately the same large decoupling parameter ( a > 4) as has been found in 173,175Lu.

Isomerism in 129La: Evidence for oblate nuclear shape

Using the reactions 121Sb+ 12C, 118, 119, 120Sn+ 14N, 115In+ 18O a new activity with T 1 2 = 0.56±0.05 sec was produced. It was identified as an isomeric state of 129La by analysis of excitation functions and cross bombardments. The isomeric state decays by a 104 keV (E3) −67.5 keV (M1) cascade to the ground state. The experimental data confirm recent calculations which predict for 129La an oblate equilibrium deformation.

The decay of 68Cu and 68Ga

The decay of the nucleides 68Cu and 68Ga, both populating levels in 68Zn, has been studied by means of Ge(Li) and NaI(Tl) gamma-ray detectors. The 68Cu half-life of 31.64 ± 0.98 sec and the energies of the 577.8, 805.7, 1077.4, 1262.1, 1744.8 and 1883.7 keV gamma-rays from 68Cu decay have been measured to a much greater precision than possible previously. The energies of gamma-rays from 68Ga decay have been confirmed. Gamma-gamma coincidence measurements with Ge(Li) and NaI(Tl) detectors have confirmed the existence of 578–1077 keV, 806–1077 keV, 1262-1077 keV and 1745-1077 keV cascades in 68Zn. These results and those for β-intensities and log ft values are discussed in terms of the 68Cu and 68Ga decay schemes.

A study of the decay scheme of 134I

The decay properties of 134I obtained from fission products have been investigated with NaI(Tl) and Ge(Li) detectors. Energies (and relative intensities) of the gamma rays determined from the Ge(Li) detector and NaI(Tl)-Ge(Li) coincidence studies are 136(5.0), 236(weak), 405(8.4), 433(4.2), 488(weak), 514(4.1), 541(9.8), 596(11.6), 622(10.3), 633(3.1), 644(weak), 677(7.7), 733(weak), 768(3.9), 848(100.0), 859(6.1), 873(weak), 885(69.1), 905(weak), 923(weak), 948(6.4), 976(5.4), 1041(3.2), 1073(17.1), 1103(2.3), 1138(11.8), 1458(4.3), 1615(4.7), 1743(3.0) and 1810(6.2) keV. Gamma-ray coincidence spectra with the Ge(Li) detector were obtained with six gates; the lower half, the upper half and the total peaks of gamma-ray at 0.87 and 1.80 MeV in the NaI(Tl) gamma-ray spectrum. Anisotropy measurements for the 885-848, 1073-848 and 1138-885 keV cascades were carried out, and the possible spin sequences were given. A decay scheme is proposed with energy levels (and spins) in 134Xe at 848(2 +), 1615(2 +), 1733(4 +), 1921(3,2), 2138, 2274, 2355, 2410, 2591, 2658, 2870(4.5), 3224and 3379 keV. The levels, which are populated by strong beta groups, are also confirmed by a summing spectrum measurement. The half-life of 134I was obtained to be 52.5 ± 0.1 min.

Decay of 74As

Gamma-ray spectrum and γ-γ directional correlation measurements were performed with Ge(Li) and NaIGe(Li) detector arrangements on the decay of 74As. Eleven transitions from 595.7 to 2198.4 keV were observed and fitted into levels at 595.7±0.1, 1204.3±0.1, 1463.2±1.0, 1482.6±0.5, 1697.3±1.0, and 2198.2±0.5 keV in 74 Ge and 634.8±0.1 keV in 74 Se . Directional correlation measurements were performed on the 608-596 keV 2-2-0 cascade and on the 887-596 keV cascade. In the first case, A 2 = −0.24±0.04, A 4 = 0.30±0.05. These data yielded a (7 −6 +3)% M1 admixture for the 608 keV transition. For the latter correlation, values of A 2 = 0.6±0.2 and A 4 = 1.3±0.2 were found. These values are compatible only with the 0-2-0 cascade and thus the level at 1482.6 keV has spin zero. Percent feedings and log ft values were calculated for decays to 74Ge and 74Se.

On the magnetic hyperfine field at Hf in iron and the gyromagnetic factors g K and g R of the 624 rotational band of 177 Hf

The induced magnetic hyperfine field acting on 177 Hf nuclei implanted into an iron foil by means of an isotope separator was determined by measuring the integral rotation of the 208-113 keV γ-γ directional correlation. By using the previously known values of the g factor and the lifetime of the 113 keV state of 177 Hf a value of - (286 ± 40) kOe was obtained for the effective internal field. The same source was used to measure the g factor of the 321 keV excited level in 177 Hf, which is the ground state of the K = 9/2 + [624] rotational band. The measurement of the integral rotation of the 105-208 keV cascade yielded the value of g (321) = -0.113 ± 0.038. The combination of the g factor and the M 1/ E 2 mixing ratios of the Δ I = 1 transitions in the [624] rotational band in 177 Hf, which were determined from directional correlation measurements employing Ge(Li) detectors, gave g K = -0.18 ± 0.05 and g R = 0.19 ± 0.05.

The decay of 131Cs

In a study of the level scheme of 131Cs, we have measured the γ- γ and the ce- γ directional correlations of the 496-123.7 keV and 486-133.5 keV cascades. The linear polarization at φ=90° was measured for the 496-123.7 keV and 486-133.5 keV cascades. The L-subshell ratios for the 123.7 keV transition were determined. The g-factor of the 133.5 keV level and the half-lives of the 78.7, 123.7, 133.5 and 216 keV levels were re-investigated. The spin and parity assignments derived for the 620, 133.5 and 123.7 keV levels are 1 2 +, 5 2 + and 1 2 + , respectively. The 620, 496, 486, 133.5 and 123.7 keV transitions are found to be of pure E2, pure M1, pure E2, (M1+(22±2)%E2) and pure E2 multipolarity, respectively. An upper limit of 192 ps for the half-life of the 216 keV level is obtained. The results are compared with theoretical estimates from the calculations of Kisslinger and Sorensen, of Freed and of Freed and Miles.

Decay of 40 d 103Ru and 17 d 103Pd to levels of 103Rh

The structure and properties of the levels of 103Rh have been further characterized by studying the electrons and γ-rays emitted in the decay of 40 d 103Ru and 17 d 103Pd. K-conversion coefficients of 0.0043±0.0006 and 0.0025±0.0005 have been measured for the 497 and 610 keV γ-transitions respectively and indicate positive parity for the 537 and 650 keV levels. Using a time-to-amplitude conversion system, an upper limit of 0.4 ns has been determined for the lifetime of the 93 keV level. Angular correlations have been observed for the 444-53 and 557-53 keV cascades and indicate spins of 5 2 or 7 2 for the levels at 537 and 650 keV. A weak 242 keV γ- ray from the 537 keV level to the 3 2 − level at 295 keV establishes the spin and parity of the 537 keV level as 5 2 + . The log ft values for the β − decay and E. C. decay to the levels of 103Pd have been determined and sizeable hindrances noted.

Linear polarization and γ-γ directional correlation measurements in 106Pd

In a study of the level scheme of 106Pd, we have measured the γ-γ directional correlations of the 1045-512 keV and 616-512 keV.cascades. The linear polarization correlations were measured for the 1045 -512 keV, 1050 -512 keV and 748 -1045 keV cascades. The linear polarization at Θ = 90° was measured for the 1838 -512 keV, 1200 -1046 keV, 1394 -1046 keV and 221- 1571 keV cascades. Spin, parity and multipolarity assignments are derived. A redetermination of the half-life of the 2951 keV level did not confirm the previously reported value of T 1 2 = 200 ns . Instead we found T 1 2 ≦ 2 ns .