Average excited state lifetimes in 73Br

Lifetimes in the region of 10^?16 s have been measured for excited states between 4 and 6.6 MeV in ⁷³Br. The states were produced by the β⁺(EC) decay of a mass-separated source of ⁷³Kr, and they decayed by the emission of protons or γ-rays; their lifetimes were measured by the particle X-ray coincidence technique. The data yield information on both γ-ray and proton partial widths as well as on the level density, a level density parameter-a = 13.7 MeV^?1 is obtained. With the level widths so determined, a statistical model calculation yields excellent agreement with the delayed proton spectrum if a smooth gaussian β-strength function is employed. It is concluded, however, that without the lifetime data, β-strength function information could not have been reliably extracted.     

g-factor experiments on the first excited 2 states in Ru,Pd and Cd

The g-factors of the first 2⁺ levels in ¹⁰²Ru, ¹⁰⁶Pd and ¹¹⁰Cd have been remeasured with increased accuracy, using the perturbed angular correlation method and the radio-active mother isotopes dissolved in ferromagnetic lattices. The results are g = ± 0.408 + 0.034, g = + 0.399 ± 0.029 and g = + 0.35 ± 0.07 respectively. Possible sources of error in the use of internal fields are discussed.     

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.     

After-effects in the decay of As and Hg

After-effects following internal conversion processes in the decay of ⁷⁵Se and ^197mHg are investigated. Time differential electron-γ and time integral electron-γ, γ-electron and γ-γ directional correlation measurements are performed, and a magnetic decoupling technique is used. For certain insulating source backing materials after-effects are found. Relaxation time constants for the time-dependent perturbation and recombination time constants for the ionized atoms, as well as the strength of the time-dependent internal magnetic fields are deduced.     

Level structure of the 89-neutron nucleus 153Gd: (I). Levels and gamma-transitions in 153Gd excited in the decay of 153Tb

Investigations of the properties of ¹⁵³Gd excited states populated in ¹⁵³Tb decay were continued. The following measurements were performed: coincidence spectra e^?γ with L41, K93 + L52, K110, K129 + L87 + L88 and K195 + L152 keV conversion electron lines, angular correlations of high energy γ-cascades going through the 109.7 keV level, delayed e^?γ and e^?e^? coincidence spectra to determine the half-lives of 41.5, 93.3, 109.7, 129.1,183.5, 212.0 and 216.1 keV states, R(135°, ± B) parameters of IPAC for the 102–110 and 83–129 keV cascades using ¹⁵³Tb sources implanted into Fe foil.A decay scheme of ¹⁵³Tb containing 50 excited levels is proposed. Their spins, parities, $\text{log}\text{?t}$ and, for low-lying levels, also the mean half-lives have been determined. An estimation of the g-factors of the 109.7 and 129.1 keV levels has been given. On the basis of half-lives of investigated states absolute values of reduced γ-transition probabilities for these states have been calculated. The structure of the ground state of ¹⁵³Gd is discussed.     

The decay of 91 min As

The energies and relative intensities of γ-rays following the β-decay of ⁷⁸As (and ⁷⁶As) to levels in ⁷⁸Se (and ⁷⁶Se) have been measured using an 8 cm³ Ge(Li) spectrometer. The β-decay of ⁷⁸As has been measured using a superconducting magnet beta-ray spectrometer with two 3 mm thick Si(Li) detectors. These data plus β-γ and γ-γ coincidence results have been used to construct a level scheme with 18 excited levels in ⁷⁸Se. The half-life of ⁷⁸As was measured to be 90.7±0.2 min.     

Electroexcitation of the first excited state in K

Electroexcitation of the first excited state in ³⁹K has been studied in the momentum transfer region of 0.8–2.5 fm⁻¹. Separation of the longitudinal and transverse form-factor components has been obtained. The longitudinal form factor has been analyzed model-independently. A B (M1) value for this l-forbidden transition was also obtained. Presently available theoretical predictions are unable to reproduce the B(M1) value or the transverse form-factor data.     

Lifetime of the first excited state in Zr

The reaction ⁹⁶Zr(p, p′ e) was used to measure the lifetime of the 0₂⁺(1.59 MeV) state in ⁹⁶Zr through the observation of delayed coincidences between a pulsed proton beam and the E0 internal conversion electrons. The half-life is 3.80 ± 1.5 ns. This value is compared to a simple shell model calculation.     

Analysis of the properties of excited states in 165Er

An analysis of ¹⁶⁵Tm decay has shown that precision measurements of the γ-ray and internal conversion electron intensities, in combination with angular correlation measurements, provide additional data useful for the determination of the mixing and intensity ratios of γ-transitions with a small energy difference. The spin of the 589.868 keV state is found to be $\text{I}{}^{\mathrm{\pi }}\text{=}\text{1}\text{2}{}^{\mathrm{?}}$. Doublet opposite-parity transitions from states at 1103.495, 920.632 and 745.968 keV to levels near 590 keV with an energy difference ΔE = 108 ± 22 eV are identified.     

The excited states of 85Sr

High resolution γ-ray studies have shown the decay patterns of isomers of ⁸⁵Y to be very complex. A level scheme of ⁸⁵Sr is proposed from the results of γ-γ coincidence measurements. Spin and parity assignments to the levels of ⁸⁵Sr were made on the basis of log ft values, nuclear reaction data and γ-ray branchings. The level scheme is discussed within the theoretical framework of $\text{n(}\text{g}{}_{\mathrm{<mtext>9</mtext><mtext>2</mtext>}}\text{)}{}^{\mathrm{?3}}$ cluster properties.     

Half-life measurements of excited levels in 122I

The half-lives of three low-lying levels in ¹²²I have been measured using delayed coincidence techniques. The following results were obtained: $\text{T}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{(61.8}\text{keV}\text{) = 7.4 ± 0.5}\text{ns}\text{, T}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{(90.7}\text{keV}\text{) = 1.9 ± 0.3}\text{ns and}\text{T}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{(148.8}\text{keV}\text{) ≦ 80}\text{ps}$. All transitions depopulating these levels are mainly of M1 multipolarity; they are hindered with factors up to 295 as compared to the single particle estimates.     

Nuclear lifetime measurements of some excited states in 187Re

Earlier measurements on half-lives of the 686 keV, 625 keV and 618 keV levels in ¹⁸⁷Re have shown remarkable disagreements. The main object of this investigation has been to remeasure these half-lives by means of the delayed coincidence method utilizing a long-lens electron-electron spectrometer. The half-lives of these levels were measured as being: 686 keV level: $\text{T}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{= 10±3}\text{ps}\text{; 625 keV}$ level: $\text{T}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{= 548 ± 20}\text{ps}\text{; 618 keV}$ level: $\text{T}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{<50}\text{ps}$.     

Lifetime measurement of the first excited state of 64Ga

The half-life of the first excited state of ⁶⁴Ga has been measured with a pulsed beam technique. The half-life was determined to be T_1/2 = 21.9 - 0.7 7s. The corresponding B(E2) = 13.6 - 0.4 e²fm⁴ shows good agreement with the Weisskopf estimate, i.e., 15.2 e²fm⁴, thereby establishing the 2⁺ assignment to this state and the single particle nature of the 42.89 keV transition.     

Evidence for formation of the first excited state of positronium

Evidence based on positronium 2γ annihilation radiation is reported for the formation of the n=2 state of positronium in a gas by optical excitation from the n=1 state.     

Levels in 44Ca excited by the β-decay of 44K

The β-decay of 22 min ⁴⁴K has been re-investigated with a Ge(Li) spectrometer of improved resolution and efficiency. A total of 58 γ-rays has been assigned to the decay of ⁴⁴K. Of these 53 have been incorporated into a revised decay scheme containing 20 excited states. The ⁴⁴K half-life was determined to be 22.15 ± 0.20 min.     

The excited states of Kr and Rb isotopes in the 78 ≦ A ≦ 85 mass region

The excited states of the ^{78, 80, 81}Kr and ^{80, 81, 83}Rb nuclei were investigated in radio-active decays of the respective Rb and Sr isotopes. The level schemes were established and for a number of levels the spin-parity assignments suggested on the basis of the log ft values and γ-branching ratios, as well as in some cases angular-correlation results. The structures of excited states of the odd Kr, odd Rb, and doubly even Kr isotopes are compared and discussed in the framework of existing theoretical approaches.     

Levels in 161Tm excited in the decay of 4.2 min 161Yb

The decay of ¹⁶¹Yb ($\text{T}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{= 4.2}\text{min}$) has been investigated with Ge(Li) and Si(Li) detectors and a toroidal β-spectrometer. Isobarically separated samples produced by the YASNAPP facility at Dubna Institute were used. The singles γ-ray spectrum, the conversion electron spectrum, γ-γ-τ and e-γ coincidences have been measured. In all, 67 γ-ray transitions have been observed. A decay scheme for ¹⁶¹Yb is proposed involving 12 excited states in ¹⁶¹Tm. The $\text{7}\text{2}$⁺[404], $\text{7}\text{2}$^?[523] and $\text{5}\text{2}$⁺[402] levels have been identified. The interpretation of the high-lying levels is discussed. The Q-value of ¹⁶¹Yb decay has been determined to be 3850 ± 250 keV. The A-dependence of the energies of the one-quasiparticle states in odd-A Tm isotopes is demonstrated.     

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.