On the structure of71As and 73As

The structure of the nuclei ⁷¹As and ⁷³As has been investigated by studying the decay of ⁷¹Se, ^73gSe and ^73mSe, the ⁷²Ge(p, 2nγ)⁷¹As reaction, the ⁷³Ge(p, nγ)⁷³As reaction and the ⁷²Ge(³He, d) ⁷³As reaction. Level schemes of ⁷¹As and ⁷³As are constructed on basis of the energies and intensities of the gamma transitions and their coincidence relations. Spins and parities are deduced from log ft values, l-values and the decay properties of the excited states. The measured half-life of the lowest excited state in ⁷¹As is $\text{T}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{= 59 ± 10}\text{ns}$. The experimental level-schemes are compared with the predictions of the cluster-vibrational coupling model.     

Study of 74As by the 73Ge(3He,d) reaction

The energy levels of ⁷⁴As have been studied using the ⁷³Ge(³He, d)⁷⁴As reaction at an incident energy of 17 MeV. The overall energy resolution was 30 keV. Twenty-five levels in ⁷⁴As were identified up to 2.2 MeV excitation energy and angular distributions were measured in the interval $\text{3}\text{3}\text{4}\text{°}$ to $\text{86}\text{1}\text{4}\text{°}$. Spectroscopic strengths and l_p values have been extracted for many of the transitions by means of a distorted-wave analysis of the differential cross sections. A comparison with the ⁷⁵As(p, d) data suggests the presence of several unresolved doublets in ⁷⁴As.     

Origin of the high-and low-frequency K-satellites of 31Ga, 32Ge and 33As

The origin of the high- and low-frequency K-satellites of ³¹Ga, ³²Ge, ³³ As is explain on the basis of Hayasi's theory of quasi-stationary states. It is shown that the same QSS difference gives rise to a particular satellite of either type in all the elements. The results are compared with those of multiple ionisation theory.     

Investigation of the level schemes of 73,75,77As via the (3He,d) reaction

The reactions ^{72, 74, 76}Ge(³He, d) were investigated at E_lab = 23 MeV with a multigap and a Q3D magnetic spectrograph. Some 30 new levels up to $\text{E}{}^1\text{≈ 4}\text{MeV}$ have been found. The level schemes of the odd As isotopes ^{73, 75, 77}As up to $\text{E}{}^1\text{≈ 4}\text{MeV}$ seem to be rather independent of the neutron number. The good agreement of the low-lying level structure with the Coriolis-coupling model including a pairing force was verified and the vacancies of low-lying shell model states were extracted and compared with the simple pairing theory.     

A study on the decay of ^72As

The excited states of the ⁷²Ge nucleus were investigated in radioactive decay of ⁷²As. Three new transitions with 1996.58, 2125.59 and 2255.49keV have been found for the first time. One γ-ray with 912.09keV has been placed in the decay scheme for the first time, and the placement of 1938.88, 2116.79, 2785.59, 2833.03, 2950.69 and 3338.00keV γ-rays are confirmed again in the present work. One new level at 2027.72keV excitation energy is proposed. The level scheme was established and for a number of levels spin-parity assignments are suggested on the basis of logft values and γ-branching ratios.     

The nuclear magnetic moment of 71As and 72As

Nuclear magnetic resonance of oriented ⁷¹As and ⁷²As nuclei has been observed in an iron host lattice at low temperatures. The resonance frequencies are v_l = 174.96(10) MHz and 282.00(11) MHz respectively for zero external field. Using B_h.f.(FeAs) = 342.9(3) kG the g-factors of the two isotopes are derived as $\text{g(}{}^{71}\text{As}\text{) = (+)0.6694(7)}\text{and}\text{g(}{}^{72}\text{As) = (?)1.0789(11)}$. Combining nuclear orientation data with these results the spin of ⁷¹As has been confirmed as $\text{I =}\text{5}\text{2}$. The magnetic moments of the $\text{5}\text{2}{}^{\mathrm{?}}$ and 2^? states in the As isotopes are discussed in the framework of the shell model with configuration mixing.     

Level structure of 72As studied with the (α, xnp) reaction

States of ⁷²As, excited through the ⁷⁰Ge(α, np) and ⁷²Ge(α, 3np) reactions at E_α = 30 to 55 MeV, were studied. Excitation functions, γ-ray angular distributions, γ-γ coincidences and γ-time distributions with respect to the beam bursts, were determined. Five excited states are identified with levels previously observed with the (p, n) reaction. In addition seven new levels and their decay pattern are incorporated into a level scheme. A half-life of 17 ± 3 nsec was determined for the 309.8 keV state, and evidence for the existence of a long-lived state (>100 nsec) was obtained. A simple scheme based on simple particle shell-model configurations accounts for the gross properties of the low lying levels. While definite spin and parity assignment for the upper excited states require further measurements, tentative spin values up to 7 are obtained.     

The g-factors of the first 2+ states in 50, 54Cr, 54Fe and 70Ge

The gyromagnetic ratios of the first excited J^π = 2⁺ states of ^50,54Cr, ⁵⁴Fe and ⁷⁰Ge have been determined by the ion-implantation perturbed angular correlation technique (IMPAC) with ferromagnetic Gd as stopping material. The g-factors were extracted from the measured precession angles with use of known lifetimes, static hyperfine magnetic fields and transient hyperfine magnetic field data for fast ions traversing ferromagnetic lattices. The deduced values are 0.59 ± 0.10, 0.56 ± 0.10, 1.08±0.19 and 0.38±0.08, respectively. With the exception of ⁵⁴Fe all g-factors are close to the collective value. A re-evaluation of earlier IMPAC data on ^{70, 72, 74, 76}Ge with Fe as stopping material has been performed. The value obtained for ⁷⁰Ge is in good agreement with the one measured in this work.     

Quadrupole nuclear interactions on 73As nuclei in a Ge matrix

Large quadrupole interactions produced in Ge by radiation damage following the ⁷²Ge(α, 3n) ⁷³Se reaction are measured by TDPAC at 77 and 300 K. A strong dependence of the quadrupole frequencies with the time intervals after the end of the α irradiation is observed.     

An investigation of 73As energy levels by means of (p,n) and (p,nγ) reactions

The energy levels of ⁷³As were studied by means of the ⁷³Ge(p, n)⁷³As reaction at proton energies between 2.1 and 3.3 MeV. Neutron energies were measured by time of flight, and γ-ray energies with Ge(Li) detectors. The γ-decay of levels was studied by means of γ-n coincidences. Angular distributions were measured for the strongest de-excitation γ-rays, and relative excitation strengths of levels were derived from the neutron spectra. These are compared with predictions of the statistical theory to derive spins for a number of levels. A level and decay scheme for ⁷³As up to 1.98 MeV excitation is presented.     

A study of the 75As(n,n'γ)75As reaction

The de-excitation gammas following the inelastic scattering of neutrons from ⁷⁵As have been studied for incident neutron energies from 1300 to 2800 keV in steps of 100 keV. The energy levels and the branching ratios of their decays have been deduced from excitation function measurements: 58 energy levels have been found in the excitation energy region below 2.8 MeV, twelve of which are reported for the first time in this work. The experimental excitation functions and angular distributions have been compared with the theoretical predictions based on the statistical theory of the compound nucleus. Spin and parity assignments for the levels and multipolarities for the decays are proposed for excitation energies of levels up to 2300 keV.     

Nuclear magnetic resonance of 55Mn and 75As in MnAs

Four sets of NMR signals, two each, from ⁵⁵Mn and ⁷⁵As nuclei have been observed. The temperature dependences of ⁵⁵Mn resonances have been studied from 77 to 311 K and that of ⁷⁵As, from 77 K to about 250 K. The results show that there is a phase transition at T₁ ≈ 220 K. This transition may be due to introduction of a local spontaneous distortion in the region of the domain walls in the lattice, resulting in lowering of symmetry at low temperatures. Another possibility is the canting of spins which would lower the magnetic group symmetry. The observed resonances have been assigned to arise from the nuclei at the edge and the centre of the domain walls at temperatures T >T₁ and from two types of wall edges with inequivalent orientation of atomic spins at T < T₁. The isotropic hyperfine field at 0 K obtained by extrapolating the resonance frequencies are 227 and 285.1 kOe at ⁵⁵As nuclei, respectively. The anisotropy in the hyperfine field is nearly zero at ⁵⁵Mn nuclei and about 5.8 kOe at ⁷⁵As nuclei at 0 K.     

Mass and excited levels of the neutron-rich nuclei 73Zn and 74Zn studied with the 76Ge(14C, 17O) and (14C, 16O) reactions

The ⁷⁶Ge(¹⁴C, ^{16, 17}O)^{74, 73}Zn reactions have been studied at 72 MeV bombarding energy. The mass excesses of ⁷³Zn and ⁷⁴Zn were determined to be ?65.41 ± 0.04 and ?65.62 ± 0.04 MeV, respectively. In addition, previously unknown excited levels were identified in both nuclei. The structure of ⁷³Zn is discussed in terms of HFB calculations.     

Properties of 81Kr levels populated in the decay of 81Rb isomers

The β⁺ decay of ⁸¹Rb ground and isomeric states (4.58 h and 30.25 min) have been studied with Ge(Li) detectors in both singles and coincidence modes. The decay of the ⁸¹Rb isomer ($\text{T}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{= 30.25 ± 0.25}\text{min}$) has been investigated for the first time. The relative electron intensities of fourteen transitions in ⁸¹Kr have been measured with a magnetic Si(Li) spectrometer and an iron-free toroidal magnetic spectrometer. The internal conversion coefficients have been determined by the normalized electron-to-γ-ray ratio method. The multipolarities of the transitions were deduced. The spin-parity assignments have been made from the consideration of the logft values, the transition multipolarities and the γ-rays branching ratios. The structure of some of the excited states in the ⁸¹Kr nucleus is discussed.     

An investigation of the level scheme of 72As through the 72Ge(p,nγ)72As reaction

The level scheme of the doubly odd nucleus ⁷²As has been investigated by the (p, nγ) reaction up to an excitation energy of about 800 keV. Spin and parity assignments were made by measuring internal conversion coefficients and by an analysis of the (p, n) cross sections through the statistical model of the compound nuclear reaction. The level scheme obtained was interpreted by a simple model calculation based on the shell model.     

The complex transfer reaction (14C, 15O) on Ni,Zn and Ge targets: Existence and mass of 69Ni

The (¹⁴C, ¹⁵O) complex transfer reaction has been studied at 72 MeV incident energy on ^58,60,62.64Ni ^68,70Zn and ^74,76Ge targets. Spectra and differential cross sections have been measured in a 5° angular range centred around a laboratory angle of 6°. The nucleus ⁶⁹Ni has been observed for the first time and its mass determined.     

Measurement of the parity non-conservation in nuclear forces in 75As, 171Tm,and 175Lu and of the polarized bremsstrahlung from 51Cr, 170Tm, 177Lu,and 198Au

The circular polarization P of γ-rays from unpolarized sources of ⁷⁵Se, ¹⁷¹Er, and ¹⁷⁵Yb of strengths ? 500 Ci has been measured with a Compton polarimeter of the radial transmission type. Eight NaI crystals and a four-fold current integration system were used to simultaneously record the data in four independent channels. The results are: P = ?(1.8 ± 6.0) × 10^?5 for the 401 keV transition in ⁷⁵As (the experimental error is ± 1.5 × 10^?5, the remaining part is due to the uncertainty in the decay scheme of ⁷⁵Se), P = (0.8 ± 1.5) × 10^?4 for the 296 keV and 308 keV transition in ¹⁷¹Tm, and P = (5.7 ± 0.8) × 10^?5 for the 396 keV transition in ¹⁷⁵Lu. The last value confirms the parity non-conservation in nuclear forces. The polarimeter was calibrated with bremsstrahlung from ¹⁷⁰Tm. The correction for polarized bremsstrahlung was given special attention. Correction factors are derived for ⁵¹Cr, ¹⁷⁷Lu, and ¹⁹⁸Au from a comparison of the measured and calculated bremsstrahlung yields.     

Investigation of the reaction 37Cl(n, γ)38Cl

With Ge(Li) detectors the γ-radiation following thermal-neutron capture in natural and in ³⁷Cl enriched targets was studied. A total of 79 γ-lines has been assigned to the ³⁷Cl(n, γ) reaction and 64 of these lines have been placed in a decay scheme of ³⁸Cl. The excitation energies of 24 bound states of ³⁸Cl have been determined with 0.09–1.2 keV errors. The neutron separation energy of ³⁸Cl is 6107.7 ± 0.4 keV. A strong correlation between reduced stripping widths and (n, γ) primary reduced widths was found for the l_n(d, p) = 1 states if, instead of the Weisskopf reduction factor E_γ^?3, a factor E_γ^?1.2 was used.     

The (d, 6Li) reaction on 12C, 16O, 24Mg, 40Ca and 58Ni at 54.25 MeV

The (d, ⁶Li) reaction was studied at E_d = 54.25 MeV on the target nuclei ¹²C, ¹⁶O, ²⁴Mg, ⁴⁰Ca and ⁵⁸Ni. The data were analyzed with finite-range DWBA calculations. The absolute values of the α-cluster spectroscopic factors and the target mass dependence of the relative S_α were in agreement with those in the (p, pα) reaction at E_p = 100 and 157 MeV. The theoretical calculations of the relative S_α were in better agreement with the experimental data at higher energy than at the lower energies.     

Beta decays of 25Na, 25Al and 29Al

The radioactivities ²⁵Na, ²⁵Al, and ²⁹Al were produced in the ²³Na(t, p)²⁵Na, ²⁴Mg(d, n)²⁵Al, and ²⁷Al(t, p)²⁹Al reactions using a 3.5 MV Van de Graaff. γ-radiations were measured by means of a target-transfer system and a Ge(Li) detector with or without Compton suppression. Decay schemes derived for ²⁵Na and ²⁹Al are in general agreement with earlier results, but with improved accuracy of branching ratios and much sharper limits on the intensities of certain unobserved β- and γ-ray transitions. Precision measurements of the energies of principal γ-rays gave results in keV for the listed decaying bodies as follows: ²⁵Na ? 1611.716(11); ²⁵Al ? 1611.708(11); and ²⁹Al ? 1273.361(9). The energy determinations of the ²⁵Mg 1612 keV γ-transition measured in the decays of ²⁵Na and ²⁵Al differ by 8 ± 9 eV.