Angular Correlation Studies Research Articles

A new nuclear chemical approach to the study of malignancy using perturbed angular correlations.

A new nuclear chemical approach to the study of malignancy using perturbed angular correlations.

Positron angular correlation studies of phase transitions in ammonium halides

The ammonium halides present an interesting system for positron angular correlation study in view of their polymorphism and the internal dynamics of ammonium ion. Cohesive energy calculations [1] have shown that ammonium ions are predominantly ionic and the hydrogen bonding contribution to cohesive energy is less than 3%. It is shown here that the positron angular correlation is very sensitive to the nature of the chemical bond of the hydrogen ion with the lattice. In the ordered phase, at a considerably lower temperature below the transition, the ammonium ion assumes a rigid configuration displaying the full effect of covalent bond. The angular correlation broadens at this phase. At higher phases the effect of covalency is washed out due to torsional oscillations and the angular correlation curve becomes narrower. But in the phase I modification of NH4I, the width of angular distribution becomes larger indicating the creation of cation vacancies due to the relative instability of the ammonium ion in this lattice. Die Ammoniumhalogenide stellen ein interessantes System fur eine Untersuchung der Positronenwinkelkorrelation im Hinblick auf ihren Polymorphismus und die innere Dynamik des Ammoniums dar. Berechnungen der Kohasionsenergie [1] haben gezeigt, das die Ammoniumionen vorwiegend ionisch gebunden sind und der Anteil der Wasserstoffbindung zur Kohasionsenergie kleiner als 3% ist. Es wird hier gezeigt, das die Positronenwinkelkorrelation gegenuber der Natur der chemischen Bindung des Wasserstoffions mit dem Gitter sehr empfindlich ist. In der geordneten Phase nimmt bei einer merklich tieferen Temperatur unterhalb des Ubergangs das Ammonium eine starre Konfiguration an, die den vollen Einflus der kovalenten Bindung zeigt. Die Winkelkorrelation verbreitert sich in dieser Phase. Bei hoheren Phasen wird der Einflus der Kovalenz infolge von Torsionsschwingungen verwaschen und die Winkelkorrelationskurve wird schmaler. Jedoch wird in der Phase I von NH4J die Breite der Winkelverteilung groser und zeigt die Bildung von Kationenleerstellen an, die durch die relative Instabilitat des Ammoniumions in diesem Gitter hervorgerufen werden.

Positron annihilation in sodium borate and calcium phosphate glasses

Positron lifetime and annihilation photon angular correlation studies have been performed in glasses of molar composition xNa2O, (1-x)B2O3. A strong dependence of the lifetime parameters on composition, x, is attributed to underlying changes in both disorder and free volume. Additional investigations of the effect of vanadium doping in a sodium borate 0.2Na2O, 0.8B2O3 glass and a calcium phosphate 0.5CaO, 0.5P2O5 glass suggest a further positronium inhibition mechanism. An interpretation based on electron scavenging by the transition metal impurities is tentatively proposed.

A study of the low-lying levels in 61Ni

Electromagnetic decay properties for seventeen states in 61Ni have been examined by means of the 58Fe(α,nγ) 61Ni reaction with E α = 8 MeV and the 60Ni(d, pγ) 61Ni reaction at E d = 6 MeV. Mean lifetimes were obtained with the Doppler-shift attenuation method. Spins, parities, and mixing ratios were determined from angular correlation studies and linear polarization measurements. The combined results permit new J π assignments of 7 2 −, 5 2 −, 7 2 −, and 9 2 + for the levels at 1016, 1611, 2020 and 2123 keV, respectively. Experimental results, including transition strengths, are compared to shell model predictions.

Angular correlation and nuclear orientation study ofI131populated in the decay ofTem131

Some additional levels are proposed in the decay scheme of $^{131}\mathrm{Te}^{m}$. From angular correlation and nuclear orientation measurements the spin and parity of several levels are determined uniquely: 774 keV (${\frac{11}{2}}^{+}$), 852 keV (${\frac{9}{2}}^{+}$), 1060 keV (${\frac{9}{2}}^{+}$), 1315 keV (${\frac{9}{2}}^{+}$), 1556 keV (${\frac{15}{2}}^{+}$), 1596 keV (${\frac{13}{2}}^{+}$), 1646 keV (${\frac{11}{2}}^{\ensuremath{-}}$), 1797 keV (${\frac{15}{2}}^{\ensuremath{-}}$), 1899 keV (${\frac{13}{2}}^{\ensuremath{-}}$), 1980 keV (${\frac{11}{2}}^{\ensuremath{-}}$), and 2001 keV (${\frac{9}{2}}^{\ifmmode\pm\else\textpm\fi{}}$ or ${\frac{11}{2}}^{+}$). The $\ensuremath{\delta}(\frac{E2}{M1})$ ratios for the different transitions are obtained. The magnetic moment of the $^{131}\mathrm{Te}$ isomeric state is derived: $\ensuremath{\mu}=(\ensuremath{-}1.04\ifmmode\pm\else\textpm\fi{}0.04){\ensuremath{\mu}}_{N}$.RADIOACTIVITY $^{131}\mathrm{Te}^{m}$ from $^{130}\mathrm{Te}(n, \ensuremath{\gamma})$; measured $\ensuremath{\gamma}\ensuremath{\gamma}(\ensuremath{\theta})$, ${I}_{\ensuremath{\gamma}}(\ensuremath{\theta}, T)$. $^{131}\mathrm{I}$ deduced $J$, $n$, $\ensuremath{\delta}(\frac{E2}{M1})$; $^{131}\mathrm{Te}^{m}$ deduced $\ensuremath{\mu}$. Ge(Li) detectors.

Perturbed angular correlation study of electric quadrupole interactions in bicyclopentadienyl tantalum dichloride

A static electric-quadrupole interaction has been determined at tantalum nuclei in bicyclopentadienyl tantalum dichloride using time-differential perturbed angular correlations in the 133–482 keV γ-ray cascade in 181Ta. The magnitude of the electric-field gradient is found to be (4.8 ± 0.3) × 10 17 V/cm 2, with an asymmetry η of 0.22 ± 0.03. The electronic configuration of the tantalum is discussed in terms of the crystal structure and relative contributions of the ligands, bonding electrons and the 5d electron to the electric field gradient.

Angular correlation studies of isobaric analog states in 49Sc via the [formula omitted] reaction

A new method for studying the proton decay of isobaric analog states is proposed. The proton decay of highly excited analog states, populated by the (τ,d) reaction, is investigated using method II of Litherland and Ferguson. Spins and proton partial widths for transitions to the ground and excited states of the target are extracted by means of d- p angular correlation measurements. The method is illustrated by a study of analog states in 49Sc.

Nuclear orientation and angular correlation studies of gamma transitions in151Sm from the decay of151Pm

The levels and gamma ray transitions in 151Sm have been investigated using the two complementary techniques of directional correlation, and the directional distribution of radiation emitted by an oriented source. The orientation was produced using the hyperfine field in ferromagnetic gadolinium to polarize an ensemble of 151Pm nuclei at a temperature of 11 mK. The resultant directional distribution of the gamma rays was measured using high resolution Ge detectors. The correlation measurements used an intrinsic Ge detector in combination with a Ge(Li) detector. These two types of result enabled multipole mixing ratios to be determined for 34 gamma transitions in the decay, and unambiguous spin assignments to be made for the levels connected by these transitions. This latter information in particular should make it easier to decide whether this nucleus can be described in terms of Nilsson single particle states.

Correlations in Compound-Nucleus Decay Amplitudes in the Vicinity of Isobaric Analog States

Polarization and ($p, {p}^{\ensuremath{'}}\ensuremath{\gamma}$) angular-correlation studies near isobaric analog resonances in proton scattering from $^{92}\mathrm{Mo}$ and $^{106}\mathrm{Cd}$ indicate strong correlations between compound-nuclear decay channels. A modified Hauser-Feshbach formula which includes correlations among these channels which belong to the analog resonance can explain the data.

Angular correlation study of some highly excited levels of 16O

Angular correlation measurements at 0° involving the reaction 12C(6 Li, d)16O → α0 + 12C g.s. have been used to study several highly excited states in 16O, between 20 and 24 MeV. The method has been tested using the known 6+ at 16.3 MeV. No indication of a 8+ level was found from detailed analysis around the 20.9 broad peak; our result is in agreement with earlier assignment of 7- for this level. A spin 6 is assigned to the 21.8 level, observed in (6Li, d) and (7Li, t) data.

Perturbed alpha-gamma angular correlation studies of radon recoils into aluminium

The quadrupole interaction of 222Rn and 220Rn implanted by α-particle-decay in Al metal and Al-oxide has been investigated. The experimental results indicate an electrical interaction in cubic Al metal not in agreement with earlier measurements using isotope implanted sources.

Angular correlation study ofI129populated in the decay ofTe129

From coincidence measurements on $\ensuremath{\gamma}\ensuremath{-}\ensuremath{\gamma}$ cascades following the decay of $^{129}\mathrm{Te}^{m}$ the existence of a 1047-keV level in $^{129}\mathrm{I}$ is well established. Angular correlation measurements for several cascades give the following values: ${281\ensuremath{-}251\ensuremath{-}\mathrm{k}\mathrm{e}\mathrm{V}\phantom{\rule{0ex}{0ex}}\mathrm{c}\mathrm{a}\mathrm{s}\mathrm{c}\mathrm{a}\mathrm{d}\mathrm{e}:,{A}_{22}= 0.238\ifmmode\pm\else\textpm\fi{}0.015,,{A}_{44}= 0.014\ifmmode\pm\else\textpm\fi{}0.026;}{209\ensuremath{-}251\ensuremath{-}\mathrm{k}\mathrm{e}\mathrm{V}\phantom{\rule{0ex}{0ex}}\mathrm{c}\mathrm{a}\mathrm{s}\mathrm{c}\mathrm{a}\mathrm{d}\mathrm{e}:,{A}_{22}= 0.234\ifmmode\pm\else\textpm\fi{}0.012,,{A}_{44}= 0.011\ifmmode\pm\else\textpm\fi{}0.022;}{281\ensuremath{-}278\ensuremath{-}\mathrm{k}\mathrm{e}\mathrm{V}\phantom{\rule{0ex}{0ex}}\mathrm{c}\mathrm{a}\mathrm{s}\mathrm{c}\mathrm{a}\mathrm{d}\mathrm{e}:,{A}_{22}=\ensuremath{-}0.048\ifmmode\pm\else\textpm\fi{}0.014,,{A}_{44}=\ensuremath{-}0.014\ifmmode\pm\else\textpm\fi{}0.023;}{209\ensuremath{-}278\ensuremath{-}\mathrm{k}\mathrm{e}\mathrm{V}\phantom{\rule{0ex}{0ex}}\mathrm{c}\mathrm{a}\mathrm{s}\mathrm{c}\mathrm{a}\mathrm{d}\mathrm{e}:,{A}_{22}=\ensuremath{-}0.059\ifmmode\pm\else\textpm\fi{}0.011,,{A}_{44}= 0.018\ifmmode\pm\else\textpm\fi{}0.018;}{624\ensuremath{-}209\ensuremath{-}\mathrm{k}\mathrm{e}\mathrm{V}\phantom{\rule{0ex}{0ex}}\mathrm{c}\mathrm{a}\mathrm{s}\mathrm{c}\mathrm{a}\mathrm{d}\mathrm{e}:,{A}_{22}=\ensuremath{-}0.270\ifmmode\pm\else\textpm\fi{}0.065,,{A}_{44}= 0.047\ifmmode\pm\else\textpm\fi{}0.095;}{624\ensuremath{-}460\ensuremath{-}\mathrm{k}\mathrm{e}\mathrm{V}\phantom{\rule{0ex}{0ex}}\mathrm{c}\mathrm{a}\mathrm{s}\mathrm{c}\mathrm{a}\mathrm{d}\mathrm{e}:,{A}_{22}= 0.151\ifmmode\pm\else\textpm\fi{}0.009,,{A}_{44}= 0.003\ifmmode\pm\else\textpm\fi{}0.012;}{624\ensuremath{-}478\ensuremath{-}\mathrm{k}\mathrm{e}\mathrm{V}\phantom{\rule{0ex}{0ex}}\mathrm{c}\mathrm{a}\mathrm{s}\mathrm{c}\mathrm{a}\mathrm{d}\mathrm{e}:,{A}_{22}=\ensuremath{-}0.290\ifmmode\pm\else\textpm\fi{}0.025,,{A}_{44}=\ensuremath{-}0.002\ifmmode\pm\else\textpm\fi{}0.036;}{343\ensuremath{-}460\ensuremath{-}\mathrm{k}\mathrm{e}\mathrm{V}\phantom{\rule{0ex}{0ex}}\mathrm{c}\mathrm{a}\mathrm{s}\mathrm{c}\mathrm{a}\mathrm{d}\mathrm{e}:,{A}_{22}=\ensuremath{-}0.341\ifmmode\pm\else\textpm\fi{}0.058,,{A}_{44}= 0.033\ifmmode\pm\else\textpm\fi{}0.080.}$ These values, together with nuclear orientation data, uniquely determine the spin of the excited states at 278 keV ($\frac{3}{2}$) and 860 keV ($\frac{3}{2}$). The mixing ratios $\ensuremath{\delta}(\frac{E2}{M1})$ for the different transitions are obtained.[RADIOACTIVITY $^{129}\mathrm{Te}$ from $^{128}\mathrm{Te}(n,\ensuremath{\gamma})$; measured $\ensuremath{\gamma}\ensuremath{\gamma}$ coin, $\ensuremath{\gamma}\ensuremath{\gamma}(\ensuremath{\theta})$. $^{129}\mathrm{I}$ deduced levels, $J$, $\ensuremath{\gamma}$-mixing ratios. Enriched target, Ge(Li), Na(Tl) detectors.]

Angular correlation studies of hyperfine magnetic fields at scandium nuclei in cobalt

Hyperfine field values of −9.1 and + 1.3 T have been measured at scandium nuclei in cobalt, the positive field probably being associated with internal oxidation.

Angular correlation studies in 144Nd

The decays of 144Pr and 144Pm populate ten excited states in 144Nd. We have carried out detailed γγ angular correlation measurements in order to establish spin assignments for these levels. The measurements were performed with Ge(Li)-Ge(Li) and NaI(Tl)-Ge(Li) systems. Eleven sets of A 22 and A 44 values were obtained. The J π assignments for levels in 144Nd (level energies in keV) are as follows: g.s.,0 +; 696, 2 +; 1314, 4 + ; 1511, 3 −; 1561, 2 + ; 1791, 6 +; 2084, 2 + ; 2093, 5 −; 2186, 1 −; 2204, 4; 2644, 1. Mixing ratios were determined for six γ-transitions.

Gamma-Gamma Angular Correlation in 147Pm

Angular correlation studies have been carried out for seven cascades viz. 275-410, 275-319, 596-91, 440-91, 398-91, 319-91 and 197-398 keV in 147 Pm. Out of these 275-410 keV cascade has been attempted for the first time. A spin assignment of 5/2 + has been confirmed for the 490 keV level. The mixing ratios of 596, 440, 410, 398, 319 and 197 keV gamma rays were found to be M1+(19 -4 +6 )% E2, M1+(25 -3 +4 )% E2, E2+3.8% M3, M1+(5±1.5)% E2, M1+(1.5 -1.5 +1.0 )% E2 and M1+(82±4)% E2, respectively. The experimental transition probabilities for the 596, 440, 275, 197 and 91 keV gamma rays have been calculated and comparison made with the single particle estimates.

Finite solid angle correction factors for closed-end coaxial Ge(Li) detectors

Geometrical correction factors for a closed-end Ge(Li) detector have been computed for application to gamma-gamma angular correlation studies. The FORTRAN IV program is included in the appendix.

Angular-correlation and branching-ratio studies ofCa41with theCa40(d,pγ)Ca41reaction

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Angular correlation study of the proton decay ofN14states below 11 MeV

Angular correlations of decay protons from 15 unbound $^{14}\mathrm{N}$ states below ${E}_{x}=11$ MeV were measured in the reaction $^{12}\mathrm{C}(^{3}\mathrm{He},p)^{14}\mathrm{N}({p}^{\ensuremath{'}})^{13}\mathrm{C}_{\mathrm{g}.\mathrm{s}.}$. Incident $^{3}\mathrm{He}$ energies of 12.0, 13.5, and 14.0 MeV were used in the various measurements. The decay protons (${p}^{\ensuremath{'}}$) were detected in coincidence with reaction protons ($p$) emitted at 0\ifmmode^\circ\else\textdegree\fi{} to the beam direction. The correlations were fitted to a theoretical expression containing adjustable parameters describing the $^{14}\mathrm{N}$ substate populations and the angular momentum coupling in the $^{13}\mathrm{C}+p$ system. Where two orbital angular momenta were allowed in the decay channel, generally only the lower allowed value was considered. Our results are compared with previous work and are shown to strengthen several existing ${J}^{\ensuremath{\pi}}$ assignments. New assignments are: 10.06 MeV, ${J}^{\ensuremath{\pi}}={3}^{+}$ or $J\ensuremath{\ge}4$; 10.81 MeV, ${J}^{\ensuremath{\pi}}={5}^{+}$. The $\frac{f\ensuremath{-}}{p}$-wave mixing in the decay of the 9.17-MeV ${2}^{+}$, $T=1$ state is consistent with previous $^{13}\mathrm{C}(p,\ensuremath{\gamma})$ experiments; for the 10.43-MeV second ${2}^{+}$, $T=1$ state, ${\ensuremath{\Gamma}}_{l=3}&lt;(2.7\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}3})\ensuremath{\Gamma}$. The measured magnetic substate parameters are compared with the predictions of a simple direct-interaction model of the ($^{3}\mathrm{He},p$) reaction. A recent weak-coupling model calculation of $^{14}\mathrm{N}$ levels is reviewed in the light of the new results.[NUCLEAR REACTIONS $^{12}\mathrm{C}(^{3}\mathrm{He},p)^{14}\mathrm{N}({p}^{\ensuremath{'}})^{13}\mathrm{C}(\mathrm{g}.\mathrm{s}.)$, $E=12.0,13.5,14.0$ MeV; measured $p$, ${p}^{\ensuremath{'}}$ coin., ${I}_{{p}^{\ensuremath{'}}}({\ensuremath{\theta}}_{{p}^{\ensuremath{'}}})$, ${\ensuremath{\theta}}_{p}={0}^{\ensuremath{\circ}}$. $^{14}\mathrm{N}$-deduced $J$, $\ensuremath{\pi}$, $\ensuremath{\delta}({l}_{{p}^{\ensuremath{'}}})$, channel spin, magnetic substate populations. Magnetic spectrometer, sequential reaction.]

Beta-gamma-gamma angular correlation studies of the radiations from the decay of Sb124

Beta→ gamma→ gamma angular correlation studies are done for the following two cascades in Te124 from the decay of Sb124. (i) Beta-rays of Emax. 622 KeV → gamma-rays of 1691 KeV→ gamma-rays of 603 KeV; (ii) Beta-rays of Emax. 222 KeV → gamma-rays of 2091 KeV → gamma-rays of 603 KeV;

P33: Angular Correlation Studies of Excited States

The $^{31}\mathrm{P}(t, p)^{33}\mathrm{P}$ reaction has been used to investigate the spins and decay modes of many of the levels of $^{33}\mathrm{P}$ below an excitation energy of 6.17 MeV, as well as the multipole mixing ratios of the transitions between these levels. $\ensuremath{\gamma}$ radiation was detected simultaneously in five NaI(Tl) detectors located at angles equivalent to 5, 35, 45, 60, and 90\ifmmode^\circ\else\textdegree\fi{}, while outgoing protons were detected in an annular detector placed at 180\ifmmode^\circ\else\textdegree\fi{} with respect to the beam direction. Multiparameter techniques were used to measure the $p\ensuremath{-}\ensuremath{\gamma}$ coincidence spectra. Spin assignments were confirmed for the following levels [${E}_{x}$ (MeV) ($J$)]: $1.43(\frac{3}{2})$, $1.85(\frac{5}{2})$, $2.54(\frac{3}{2})$, $3.28(\frac{3}{2} or \frac{5}{2})$, $3.63(\frac{7}{2})$, $4.05(\frac{3}{2} or \frac{5}{2})$, $4.22(\frac{7}{2})$. Assignments were made for these levels: $3.49(\frac{5}{2})$, $4.19(\frac{5}{2})$, $4.86(\frac{3}{2})$, $5.05(\frac{3}{2})$, $5.56(\frac{3}{2})$, $5.66(\frac{1}{2}, \frac{3}{2})$, $5.73(\frac{3}{2})$.