Directional Correlations Of Gamma Rays Research Articles

Deformations and magnetic rotations in theNi60nucleus

Data from three experiments using the heavy-ion fusion evaporation-reaction Ar-36+Si-28 have been combined to study high-spin states in the residual nucleus Ni-60, which is populated via the evaporation of four protons from the compound nucleus Ge-64. The GAMMASPHERE array was used for all the experiments in conjunction with a 4 pi charged-particle detector arrays (MICROBALL, LUWUSIA) and neutron detectors (NEUTRON SHELL) to allow for the detection of. rays in coincidence with the evaporated particles. An extended Ni-60 level scheme is presented, comprising more than 270 gamma-ray transitions and 110 excited states. Their spins and parities have been assigned via directional correlations of gamma rays emitted from oriented states. Spherical shell-model calculations in the fp-shell characterize some of the low-spin states, while the experimental results of the rotational bands are analyzed with configuration-dependent cranked Nilsson-Strutinsky calculations. (Less)

Selectivity of directional correlations of gamma rays from oriented nuclear states at moderately high spins

Calculations are presented for pure-multipole cascades from an aligned initial state of moderately high spin. viz., 10. Pairs of detectors at vertices of an octant in space are used, and the question of selecting a particular assignment of spins and multipolarities from all others is investigated. It is found that for representative conditions of degree of alignment of initial state and quality of data, most of the cascades composed of combinations of dipole, quadrupole and octupole transitions can be distinguished from each other, even including in many cases the order of nonbasic transitions. The number of different cascades considered is 49. Also considered are cases simulating ultrahigh-precision data in order to illustrate principles, as well as quite low-precision data. Considered too, are cases of no alignment of initial spin, as well as the other extreme of only m = 0. A concise review of the results of the general theory of directional correlation of gamma rays from oriented initial states is given.

Conformational change in carbonic anhydrase studied by perturbed directional correlations of gamma rays

Directional correlations of gamma rays emitted by IIIIn ions at the active site of bovine carbonic anhydrase have been studied after protein conformational change caused by guanidine hydrochloride. An increase in the fraction of IIICd daughter-ions which cannot rapidly reform ligand structure following electron-capture is observed.

Directional correlations of gamma rays in 77As

Directional correlation measurements have been made for γ-transitions in 77As following the decay of 11.30 h 77Ge using two Ge(Li) detectors. Using the method of Chow et al., mixing ratios of γ-transitions and the spins of seven levels have been deduced assuming only a ground-state spin of 3 2 . Levels for which spins were deduced are 216( 3 2 ), 264( 5 2 ), 475( 9 2 ), 632( 5 2 ), 1189( 7 2 ), 1458( 3 2 ) and 1528( 5 2 ) keV .

The application of perturbed directional correlation of gamma rays to the study of protein-metal interactions.

Several branches of nuclear spectroscopy—magnetic resonance and the Mossbauer effect in particular—have been the subject of considerable interest to obtain structural and motional information about biological macromolecules. Recently, a third technique— perturbed gamma-gamma directional correlation—is being tested for the study of rotational correlation times, internal rotations and conformational changes in biological macromolecules. When two gamma rays from a radioactive nucleus are emitted in a cascade and detected with a coincidence spectrometer, the coincidence counting rate depends strongly on the angle between their directions of propagation. This directional correlation can be perturbed by the interaction of the nucleus with fields existing in macromolecules. A study of such perturbed directional correlation (PDC) has the potential to provide information on protein-metal interactions. The use of a radioactive nucleus as a rotational tracer to label macromolecules offers the possibility of obtaining information on protein structure with the sensitivity and instrumental simplicity of radioactive tracer techniques. Work to date has centered on measurement of internal electric field gradients of metalloproteins, molecular correlation times and the correlation time of water associated with proteins. This paper is a brief review of the theory and experimental technique of perturbed directional correlation of gamma rays in comparison to Mossbauer spectroscopy and the methods of magnetic resonance. Particular emphasis will be placed on the isotopes which can be used in PDC especially those which may occupy sites in biological macromolecules.

Directional Correlations of Gamma Rays inBr79

The $\ensuremath{\gamma}$ radiation following the decay of $^{79}\mathrm{Kr}$ to levels in $^{79}\mathrm{Br}$ has been studied with Ge(Li) detectors. 40 transitions were observed, including 4 which were previously unreported. $\ensuremath{\gamma}\ensuremath{-}\ensuremath{\gamma}$ directional-correlation measurements have been made using two Ge(Li) detectors. The $\frac{E 2}{M 1}$ amplitude mixing ratios for several transitions in $^{79}\mathrm{Br}$ have been determined from these directional-correlation measurements. The results of these measurements together with conversion coefficients and $log\mathrm{ft}$ values have made it possible to assign spins and parities to some of the excited levels.

Directional correlations of gamma rays in 125Sb following the decay of 9.6 d 125gSn

A decay scheme for 9.6 d 125gSn has been constructed that includes 20 previously unobserved γ-rays and two new levels. The angular correlation functions were determined for nine cascades and were utilized in conjunction with other data to establish spins and parities for nine levels. The level scheme is discussed in the context of the particle-core coupling model and the superconductor model.

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 use of the integral-bias summing coincidence spectrometer in directional correlation measurements

The performance of the integral-bias summing coincidence spectrometer (the sum-peak spetrometer) in measurements of directional correlations of gamma rays has been tested. As compared with the conventional method, the sum-peak spectrometer is easier to use and seems to yield results which agree with those obtained with the ordinary method. Because of the complex shapes of response functions of gamma rays above about 3 MeV, the new method is best suited to the study of cascading transitions below this energy, where the two methods appear to complement each other. The analysis of the sum-peak spectra in the present work is based on a simple graphical method which seems to yield satisfactory results; the use of a computer method is suggested. Some previously unknown directional correlation functions of gamma-ray cascades in 106Pd and 118Sn are also reported.

Directional Correlation of Gamma Rays in the Decay of 2·3 d 115Cd

The gamma-gamma directional correlation of the 35-493 keY cascade in the decay of 2�3 d 116Cd has been studied by the coincidence method. The results seem to favour the spin and parity assignments 1/.+, 3/.+, and 1/.- for the levels at 864, 829, and 336 keY respectively, and indicate that the 35 keY transition is (96�5�0�5)% Ml and (3�5�0�5)% E2, with a mixing parameter 8 = -0�191� 0�014. These results agree with the recent I.C.C. measurements of Backlin, Fogelberg, and Malmskog but differ from those of earlier work. Computation of the partial lifetimes of the 35 keY radiation on this basis indicates that the Ml transition is retarded by a factor of ~ 23 and the E2 transition is enhanced by a factor of ~ 958. The E 1 component of 493 ke V radiation is estimated to be hindered by a factor of ~ 4 X 10-7, while the M2 component is retarded by a factor of ~ 3. The possible collective nature of the 829 keY level is discussed.

Directional Correlations of Gamma Rays in the Decay of 36 hr 82Br

Coincidence and gamma-gamma directional correlation measurements are made for the 10 cascades of s2Kr: 1648-777, 1008-1044, 1317-777, 619-1475, 555-1317,555-619,828-1044,828-(1044)-777,698-777, and 619-698 keV, of which the cascade 1008-1044 keV has been attempted for the first time. The results permit a unique spin assignment of 5 for the 2829 ke V level from the directional correlation of the 1008-1044 keV cascade and a spin of 3 to the level at 2425 keV from that of the 1648-777 keV cascade. Multipole character and admixture are determined for the transitions 1648, 1475, 1044, 1008, 555, 828, 698, 619, and 1317 keV. Computed E2 partial half-lives for the last two transitions are compared with the predictions of the single-particle estimate and the nonaxial rotor model.

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.

Directional Correlation of the Gamma Rays ofLa140andCe140

The directional correlation of coincident gamma rays in ${\mathrm{La}}^{140}$ and ${\mathrm{Ce}}^{140}$ has been reinvestigated. Using a coincidence circuit having a resolving time of $\ensuremath{\tau}=10$ nsec, the gamma rays in coincidence with a given gamma ray, as seen by a single counter, were displayed on a multichannel analyzer. Analysis of the intensity of the lines in the coincidence spectrum was made with the help of many calibration lines and a least-squares reduction technique using an electronic computer. In ${\mathrm{Ce}}^{140}$ the following coincidences have been investigated: 923-1597, 815-1597, 487-1597, 329-1597, and 329-487 keV. In ${\mathrm{La}}^{140}$ the coincidence 162-304 keV was investigated. A discussion of the data in light of the disintegration schemes is given.

Directional Correlation of Gamma Rays Following the Decay ofEu152

Directional correlation measurements have been made on the 245 kev-122 kev, 969 kev-122 kev, 1118 kev-122 kev, 1416 kev-122 kev, 872 kev-245 kev, and 1170 kev-245 kev cascades in ${\mathrm{Sm}}^{152}$, and on the 782 kev-345 kev cascade in ${\mathrm{Gd}}^{152}$. The spins of ${\mathrm{Sm}}^{152}$ are found to be 0, 2, 4, 2, 3, 3, for the ground, 122-kev, 367-kev, 1092-kev, 1240-kev, and 1538-kev levels. The 245-kev gamma ray is found to be pure quadrupole; the 872-kev gamma ray is 98% quadrupole, 2% dipole; the 969-kev gamma ray is 98% quadrupole, 2% dipole; the 1118-kev gamma ray is 99.8% quadrupole, 0.2% dipole; the 1170-kev gamma ray is 98% quadrupole, 2% dipole; the 1416-kev gamma ray is 15% quadrupole, 85% dipole. In ${\mathrm{Gd}}^{152}$ the spin of the 1127-kev level is found to be 3 and the 782-kev gamma ray is found to be pure dipole. A spin assignment of 1, 2, or 3 for the 757-kev level would not be inconsistent with the data. For any of these cases the 412-kev gamma ray must be mostly dipole; the quadrupole content must be less than 15%.

Directional Correlations of Gamma Rays in Te124

The directional correlations of the 2.11–0.605 Mev and 1.71–0.605 Mev gamma-gamma cascades in Te 124 have been measured by using a coincidence spectrometer newly designed. Both of the correlation functions are compatible with the sequence 3 (D, Q) 2 (Q) 0, where quadrupole admixture in the first radiation is expected to be very small. The false coincidences occurring in this type of circuit are also described in some details.

Directional Correlation of Gamma Rays fromSn116

The directional correlations of successive gamma rays from ${\mathrm{Sn}}^{116}$ have been measured. ${\mathrm{Sn}}^{116}$ decays via 1.09-Mev---1.27-Mev, 1.49-Mev---1.27-Mev, 0.80-Mev---1.27-Mev and 0.40-Mev---2.09-Mev gamma cascades following beta decay from 54-minute ${\mathrm{In}}^{116m}$. The measured directional correlation functions are in agreement with those expected for $4(Q)2(Q)0$, $4(Q)2(Q)0$, 2(10% $D$, 90% $Q$, 0\ifmmode^\circ\else\textdegree\fi{} phase) $2(Q)0$ and 2(4% $D$, 96% $Q$, 0\ifmmode^\circ\else\textdegree\fi{} phase) $2(Q)0$ spin sequences, respectively.