Electromagnetic transitions in some doubly odd deformed nuclei

Nanosecond lifetimes of excited states in doubly odd deformed nuclei have been determined by in-beam measurements applying the method of delayed γ-γ coincidences as well as by experiments in the radioactive decay with the method of delayed γ-ce coincidences, respectively. Analysing the time distributions and delayed γ-ray spectra, the following half-lives of isomeric states could be obtained for the first time: $\text{T}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{(63.7}\text{keV in}{}^{160}\text{Tb}\text{) = 60 ± 5}\text{ns}\text{, T}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{(138.7}\text{keV in}{}^{160}\text{Tb}\text{) = 5.7 ± 0.5}\text{ns}\text{, T}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{(82.0}\text{keV in}{}^{156}\text{Ho}\text{) = 1.25 ± 0.20}\text{ns}\text{, T}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{(87.2}\text{keV in}{}^{156}\text{Ho}\text{) = 58.5 ± 3.5}\text{ns}\text{, T}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{(139.2}\text{keV in}{}^{158}\text{Ho}\text{) = 1.85 ± 0.10}\text{ns}\text{, T}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{(38.3}\text{keV in}{}^{162}\text{Ho}\text{) = 1.2 ± 0.2}\text{ns}\text{, T}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{(179.9}\text{keV in}{}^{162}\text{Ho}\text{) = 8.7 ± 0.2}\text{ns}\text{, T}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{(342.8}\text{keV in}{}^{164}\text{Ho}\text{) = 2.6 ± 0.2}\text{ns}\text{, T}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{(295.1}\text{keV in}{}^{166}\text{Ho}\text{) = 1.10±0.15}\text{ns}\text{, T}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{(44.6}\text{keV in}{}^{162}\text{Tm}\text{) = 1.40±0.15}\text{ns}\text{, T}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{,(163.4}\text{keV in}{}^{162}\text{Tm}\text{) = 1.1 ± 0.1}\text{ns}\text{, T}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{(220.1}\text{keV in}{}^{178}\text{Ta}\text{) = 8.5 ± 1.0}\text{ns}\text{, T}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{(289.5}\text{keV in}{}^{178}\text{Ta}\text{) = 2.0 ± 0.5}\text{ns}\text{, T}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{(392.8}\text{keV in}{}^{178}\text{Ta) ≈ 1 ns, T}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{(316.5}\text{keV in}{}^{186}\text{Re}\text{) = 0.20 ± 0.10}\text{ns}\text{, T}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{(300.2}\text{keV in}{}^{188}\text{Re}\text{) = 1.5 ± 0.2}\text{ns and}\text{T}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{(482.2}\text{keV in}{}^{188}\text{Re}\text{) = 0.26 ± 0.10}\text{ns}$. Furthermore, upper limits for the half-lives of fifteen excited states in ¹⁶⁰Tb, ^{164, 166}Ho and ^{186, 188}Re have been estimated. For eight isomeric levels in ^{186, 188}Re, the lifetimes earlier determined have been remeasured. Unlike previous studies, the existence of isomeric states at 87.2 keV in ¹⁵⁶Ho and at 179.9 keV in ¹⁶²Ho is suggested. Absolute γ-ray transition probabilities are deduced and compared with single-particle estimates according to Weisskopf and Nilsson, the latter also including pairing correlations. The K-, Ω- and f-forbidden transitions can qualitatively be explained in terms of configuration mixings. Experimental El, ΔK= 1 transition matrix elements in odd-odd deformed nuclei are supposed to be appreciably influenced by higher-order vibrational admixtures coupled via RPC and p-n interaction mixings.     

Electromagnetic transitions in some odd-neutron deformed nuclei

Using the reactions ^{155, 157}Gd(α,2n), ¹⁷⁸Hf(n,γ) and ^{177Hf(α, 2n}, the following half-lives of excited nuclear states have been measured: $\text{T}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{(188.1}\text{keV in}{}^{157}\text{Dy}\text{) = 1.00 ± 0.15}\text{ns}$, $\text{T}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{(161.9}\text{keV in}{}^{157}\text{Dy}\text{) = 1.3 ± 0.2 μ}\text{S}$, $\text{T}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{(177.6}\text{keV in}{}^{159}\text{Dy}\text{) = 9.0 ± 0.5}\text{ns}$, $\text{T}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{(614.3}\text{keV in}{}^{179}\text{Hf}\text{) = 0.50 ± 0.15}\text{ns}$, $\text{T}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{(720.7}\text{keV in}{}^{179}\text{Hf}\text{) ≦ 0.3}\text{ns}$, $\text{T}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{(516.4}\text{keV in}{}^{179}\text{Hf}\text{) < 0.2}\text{ns and}\text{T}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{(309.0}\text{keV in}{}^{179}\text{W}\text{) = 1.53 ± 0.10}\text{ns}$. A Ge(Li) timing system was employed. Electromagnetic transition probabilities are calculated in the Nilsson model including pairing and band mixing effects. Comparisons between theoretical and experimental results are performed.     

Two-quasiparticle excitations and collectivity in the weakly-deformed transitional isotopes 104, 106, 108Cd

Using the generalized centroid-shift method on the Rutgers tandem, the following half-lives of ¹⁰⁶Cd excited states were measured in the reaction ⁹³Nb(¹⁶O, p2n): $\text{T}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{(3679.0}\text{keV}\text{) = 0.7}{}^{\mathrm{+0.1}}{}_{\mathrm{?0.3}}\text{ns}\text{, T}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{(3507.8}\text{keV}\text{) = 1.2 ± 0.4}\text{ns}\text{, T}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{(3044.2}\text{keV}\text{) = 0.4 ± 0.1}\text{ns, and}\text{T}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{(2330.7}\text{keV}\text{) = 0.6 ± 0.2}\text{ns}$. With the same method applied on the Rossendorf cyclotron, the following half-lives were measured in the reactions ${}^{\mathrm{102,\; 106}}\text{Pd}\text{(α, 2}\text{n}\text{): T}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{(2902.0}\text{keV}\text{) = 0.8}{}^{\mathrm{+0.2}}{}_{\mathrm{?0.1}}\text{ns}\text{(}{}^{104}\text{Cd}\text{)}$ as well as $\text{T}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{(3737.3}\text{keV}\text{) = 0.2 ± 0.1}\text{ns}$, $\text{T}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{(3223.7}\text{keV}\text{) = 0.2 ± 0.1}\text{ns}$, $\text{T}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{(3057.4}\text{keV}\text{) = 0.10 ± 0.05}\text{ns}$, $\text{T}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{(2975.3}\text{keV}\text{) = 0.15 ± 0.10}\text{ns}$, $\text{T}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{(3110.5}\text{keV}\text{) = 0.3 ± 0.1}\text{ns}$, and $\text{T}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{(2565.2}\text{keV}\text{) = 0.2 ± 0.1}\text{ns}\text{(}{}^{108}\text{Cd}\text{)}$. The results reveal the non-collective (two-quasiparticle) character of several states above 2.9 MeV in ^{104, 106, 108}Cd, in qualitative accordance with predictions of the slightly-deformed-rotor model. They concern completely aligned [h_{$\text{11}\text{2}$}g_{$\text{7}\text{2}$}] (9^??11^?-13^?, etc.) as well as semi-decoupled [h_{$\text{11}\text{2}$}d_{$\text{5}\text{2}$}] (6^?-8^?-10^?, etc.) two-quasineutron band structures. Further, the possible character of 8⁺ (two-quasiproton) excitations, 5⁺ (two-quasineutron) states and of other intrinsic excitations is discussed. The experimental findings present a challenge to current theories of transitional nuclei for a quantitative treatment of absolute γ-ray transition strengths.     

Transition probabilities in the doubly odd nuclei 176Lu and 182Ta

The depopulation of isomeric states in ¹⁷⁶Lu and ¹⁸²Ta was studied in the (n, γ) reaction by means of delayed γ-γ coincidence measurements with NaI(Tl) and Ge(Li) detectors. The following half-lives, unknown so far, have been obtained for ¹⁷⁶Lu: $\text{T}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{(198.0}\text{keV}\text{) = 35.0 ± 1.0}\text{ns}$, $\text{T}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{(638.8}\text{keV}\text{) = 8.0±1.0}\text{ns}$ and $\text{T}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{(662.1}\text{keV}\text{) = 6.3±0.5}\text{ns}$; and for ¹⁸²Ta: $\text{T}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{(270.4}\text{keV}\text{) = 1.2 ± 0.2}\text{ns}$, $\text{T}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{(402.6}\text{keV}\text{) = 1.00 ± 0.05}\text{ns}$ and $\text{T}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{(443.6}\text{keV}\text{) = 2.2 ± 0.2}\text{ns}$. The existence of the isomeric level at 443.6 keV in ¹⁸²Ta was confirmed. Weisskopf hindrance factors have been deduced for the K- and Ω-forbidden transitions. The K-allowed transitions are considered in terms of the Nilsson model taking into account pairing correlations. The experimental results for the transitions de-exciting the 270.4 keV level in ¹⁸²Ta agree with earlier model predictions including band mixing effects. The influence of the pairing effect on K-allowed E1 transitions in doubly odd nuclei is demonstrated.     

Some M1 transition strengths in odd-A nuclei away from closed shells

By the in-beam application of the generalized centroid shift method, nanosecond half-lives have been determined for the first time: in ${}^{101}\text{Pd}\text{T}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{(1337.4}\text{keV}\text{) = 1.2}{}^{\mathrm{+0.6}}{}_{\mathrm{?0.3}}\text{ns and}\text{T}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{(261.0}\text{keV}\text{) = 0.7 ± 0.2}\text{ns}$ using the reaction $\text{(}{}^{12}\text{C}\text{,x}\text{n}\text{)}$, in ${}^{71}\text{As}\text{T}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{(147.5}\text{keV}\text{) = 0.85 ± 0.25}\text{ns}$ using the reaction (¹⁶ O, αp), in ${}^{91}\text{Nb}\text{T}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{(5455.3}\text{keV}\text{) = 1.2 ± 0.3}\text{ns}$ using the reaction (¹⁶O,2np), in ${}^{103}\text{Pd}\text{T}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{(244.0}\text{keV}\text{) < 0.2}\text{ns}$ and in ${}^{91}\text{Nb}\text{T}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{(3110.2}\text{keV}\text{) < 0.2}\text{ns}$ using the reaction P(α, xn). Some known nanosecond isomers in different nuclei produced as by-products have also been detected. In the nuclei investigated far away from closed shells with complex wave functions, M1 transitions are considered which would be l-forbidden in the pure shell model. A retarded $\text{Ml}\text{(+}\text{E}\text{2)}\text{25}\text{2}{}^{\mathrm{+}}\text{→}\text{23}\text{2}{}^{\mathrm{+}}$ transition in ⁹¹ Nb is considered as proceeding between possible multiparticle-hole configurations.     

Remeasurement of the low-energy cross section for the 15N(p, α0)12C reaction

The cross section for the ${}^{15}\text{N(p}\text{, α}{}_0\text{)}{}^{12}\text{C}$ reaction has been measured at θ_lab = 135° over the proton energy range 93 ≦ E_p ≦ 418 keV. The results are in good agreement with the less precise but much earlier measurements of Schardt, Fowler and Lauritsen (1952). An analysis of the present data in terms of a two-level calculation including the 338 keV (1^?) and 1028 keV (1^?) resonances determines a zero-energy intercept for the astrophysical S-factor of S(0) = 78 ± 6 MeV · b.     

Magnetic moments of Jπ = 192− mirror states in 43Ti and 43Sc

The time-differential perturbed angular distribution method was used to determine the g-factors of the $\text{(}\text{f}{}_{\mathrm{<mtext>7</mtext><mtext>2</mtext>}}\text{)}{}^3\text{19}\text{2}{}^{\mathrm{?}}$ states in ⁴³Ti and ⁴³Sc. The results for the mass 43 mirror pair are: ${}^{43}\text{Ti}\text{: g = 0.760 ± 0.001, T}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{, = 560 ± 6}\text{ns}$, ${}^{43}\text{Sc}\text{: g = 0.3286± 0.0007, T}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{= 473 ± 5}\text{ns}$. Considering in addition the magnetic moments in A = 41 and 42, it is suggested that the deformed states considered by Johnstone and Castel and by Erikson are responsible for the observed large deviations from the Schmidt values.     

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.     

Lifetimes and g-factors of the 6− and 7− isomers in 66Ga and 68Ga

The 6^? and 7^? isomeric states in ⁶⁶Ga and ⁶⁸Ga at 1440.9 and 1229.6 keV, respectively, have been populated with the (¹³C, 2np) and (¹⁵N, n2p) reactions on natural Fe. The half-lives of these states have been measured to be $\text{T}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{(6}{}^{\mathrm{?}}\text{,}{}^{66}\text{Ga}\text{) = 57.3 ± 1.2}\text{ns}$ and $\text{T}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{(7}{}^{\mathrm{?}}\text{,}{}^{68}\text{Ga}\text{) = 64 ± 2}\text{ns}$. Using previous data on the hyperfine field of Ga in Fe, the g-factors of these states have been determined by means of the TDPAD method. The results are $\text{g(6}{}^{\mathrm{?}}\text{,}{}^{66}\text{Ga}\text{) = 0.129 ± 0.003}$ and $\text{g(7}{}^{\mathrm{?}}\text{,}{}^{68}\text{Ga}\text{) = 0.105 ± 0.003}$. These values are in very good agreement with the independent particle model if one assumes the and configurations and uses the empirical proton and neutron g-factors from odd-A neighboring nuclei instead of the Schmidt values. The large disagreements with experiment when Schmidt values are used show that core polarization effects are important in these nuclei.     

Absolute E1, ΔK = 1 transition probabilities between multi-quasiparticle high-spin states in 176Hf and 178Hf

Applying the generalized centroid shift method in (α, 2n) reactions, the half-lives of the 3080 keV 15⁺ state in ¹⁷⁶Hf and of the 1637 keV 5^? state in ¹⁷⁸Hf have been measured as $\text{T}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{= 0.20}{}^{\mathrm{+0.12}}{}_{\mathrm{?0.08}}\text{ns}$ and $\text{T}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{= 0.40 ± 0.10}\text{ns}$, respectively. B(El) values of K-allowed E1 transitions $\text{n}\text{9}\text{2}{}^{\mathrm{+}}\text{[624]→}\text{7}\text{2}{}^{\mathrm{?}}\text{[514]}$ are derived, and together with other data on similar transitions in odd-A nuclei, compared with predictions of the Nilsson plus pairing model. In ¹⁷⁶Hf, the 15⁺ and 14^? states at 3080 and 2866 keV, respectively, appear as quite pure deformed 4QP configurations. In the 2QP state at 1637 keV in ¹⁷⁸Hf, possible strong mixing of vibrational components is discussed coupled via 2QP K-admixtures arising from the partial alignment of the $\text{i}{}_{\mathrm{<mtext>13</mtext><mtext>2</mtext>}}$ neutron.     

Nuclear orientation study of the excited states of 129I populated in the decay of 129gTe and 129mTe

From the angular distributions of γ-rays emitted by oriented ^129gTe and ^129mTe nuclei implanted in iron by isotope separator, unique spin assignments could be made for the excited states of ¹²⁹I at 487.4 keV $\text{(}\text{5}\text{2}{}^{\mathrm{+}}\text{)}$, 696.0 keV $\text{(}\text{11}\text{2}{}^{\mathrm{+}}\text{)}$, 729.6 keV $\text{(}\text{9}\text{2}{}^{\mathrm{+}}\text{)}$, 768.9 keV $\text{(}\text{7}\text{2}{}^{\mathrm{+}}\text{)}$, 1050.4 keV $\text{(}\text{7}\text{2}{}^{\mathrm{+}}\text{)}$ and 1111.8 keV $\text{(}\text{5}\text{2}{}^{\mathrm{+}}\text{)}$. In addition, E2/M1 amplitude ratios for the following ¹²⁹I γ-rays (energies are in keV) are derived: δ(459.6) = ?(0.076^+0.037_?0.148); δ(487.4) = 0.50^+0.17_?0.10 or δ^? = 0.35^+0.15_?0.09; δ(556.7) = 0.06±0.02 or δ^? = ?(0.10±0.02); δ(624.4) = 0.10±0.26 or δ^? > 0.4; the 696.0 keV γ-ray is pure E2; δ(729.6) = ?(0.34±0.06) or δ^?1 = 0.55±0.05; δ(741.1) = ?(0.27±0.10) or δ^?1 = ?(0.43±0.12); δ(817.2) = 0.46±0.04 or δ^?1 =0.20±0.03 if $\text{I}{}^{\mathrm{\pi }}\text{(845}\text{keV}\text{) =}\text{7}\text{2}{}^{\mathrm{+}}$; δ(1022.6) = ?(0.02 ±0.02) or δ^?1 = ?(0.23±0.02); $\text{δ(1084) = 0.56}{}^{\mathrm{+0.04}}{}_{\mathrm{?0.14}}$; δ(1111.8) = 0.06±0.05 or δ^?1 = ?(0.08±0.05). The anisotropy of the 531.8 keV γ-ray excludes $\text{1}\text{2}{}^{\mathrm{+}}$ as a possible spin assignment for the 559.6 keV level, so that no $\text{1}\text{2}{}^{\mathrm{+}}$ level is fed in the decay from ¹²⁹Te. Anisotropies for the 209, 250.7, 278.4 and 281.1 keV γ-rays are also measured. Comparison of the level scheme is made with theoretical predictions from both the pairing-plus-quadrupole model and the intermediate coupling unified model.     

The measurement of the rotational relaxation times of OCS from the nutation signals

The time dependence of microwave absorption was measured for the J = 2-1 and J = 3-2 transitions of OCS under on- and off-resonant conditions utilizing Stark and source modulation, respectively. The two effective pressure parameters obtained under the two conditions, which correspond to $\text{(T}{}_2{}^{\mathrm{?1}}\text{+ T}{}_1{}^{\mathrm{?1}}\text{)}\text{4πP}$ and $\text{(2πT}{}_2\text{P)}{}^{\mathrm{?1}}$, respectively, according to the Bloch equation, are different beyond experimental error; the difference $\text{(T}{}_2{}^{\mathrm{?1}}\text{? T}{}_1{}^{\mathrm{?1}}\text{)}\text{2πP}$ is 0.94 ± 0.38 (2.5σ) MHz/Torr for J = 2?1. This difference was also determined to be 1.19 ± 0.30 MHz/Torr from the dependence of the nutation frequency on the microwave power.     

Lifetimes of the Si I 3p4s 1P1 and 3p3d 1P1 states

A beam of metastable silicon atoms was produced by collisional dissociation of silicon molecules and selectively excited by a pulsed dye laser. The lifetimes of the excited Si I states were directly determined from the fluorescence decay curve: $\text{τ(3p4s}{}^1\text{P}{}_1\text{) = 4.1 (4) ns}$, $\text{τ(3p4s}{}^3\text{P}{}_2\text{) = 4.4 (4) ns}$, $\text{τ(3p3d}{}^1\text{P}{}_1\text{) = 8.1(5) ns}$.     

Isomeric E1 and M1 transitions in 177Ta and in neighbouring odd-A Lu and Ta isotopes

Delayed γ-ray spectra as well as time distributions have been measured applying the r.f.-γ method and the method of delayed γ-γ coincidences. Using the reaction ¹⁷⁵Lu(α, 2n)¹⁷⁷Ta, the half-lives of the levels at 70.6 and 73.6 keV in ¹⁷⁷Ta have been determined as $\text{T}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{= 80±10}\text{ns}$ and $\text{T}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{= 370±50}\text{ns}$, respectively. In further experiments, upper limits for the lifetimes of the $\text{9}\text{2}{}^{\mathrm{?}}\text{[514]}$ and $\text{5}\text{2}{}^{\mathrm{+}}\text{[402]}$ states in ¹⁷¹Lu and ¹⁷³Lu were estimated. Comparisons of the experimental half-lives to Weisskopf and Nilsson model predictions are performed taking into account pairing correlations. For the calculations, a modified Nilsson Hamiltonian has been used. The hindrance factors obtained are summarized together with those deduced for corresponding transitions in neighbouring odd-proton nuclei. From the experimental results in ¹⁷⁷Ta, conclusions have been drawn on the possible value of the constant k₂ occurring in the magnetic dipole operator.     

Hyperfine structure of CH3OH

Hyperfine structure of the (0, 0, 1) - (1, 0, 1) transition of methanol has been investigated by beam absorption and of the (J, 1, 3?) → (J, 1, 3+) transitions for J = 2, 3, and 6 by beam-maser spectroscopy. The best-fit results for the spin-rotation and spin-spin coupling constants $\text{C}{}_{\mathrm{JK\tau \pm }}{}^{\mathrm{(i)}}$ and $\text{D}{}_{\mathrm{JK\tau \pm }}{}^{\mathrm{(i)}}$, respectively, are in kHz¹: $\text{C}{}_{101}{}^{\mathrm{(1)}}\text{= 2.4(10)}$, $\text{C}{}_{101}{}^{\mathrm{(2)}}\text{= ?0.6(10)}$, $\text{D}{}_{101}{}^{\mathrm{(1)}}\text{= ?13.8(9)}$, $\text{D}{}_{101}{}^{\mathrm{(2)}}\text{= 7.0(9)}$, $\text{C}{}_{\mathrm{213?}}{}^{\mathrm{(1)}}\text{= ?5.0(10)}$, $\text{C}{}_{\mathrm{213?}}{}^{\mathrm{(2)}}\text{= ?5.5(10)}$ and ($\text{C}{}_{\mathrm{J13?}}{}^{\mathrm{(2)}}\text{- C}{}_{\mathrm{J13+}}{}^{\mathrm{(2)}}\text{) = 0.98(9)}$.     

Interference effects in 12C(p, γ)13N and direct capture to unbound states

Excitation functions of the capture reaction ¹²C(p, γ₀)¹³N have been obtained at θ_γ = 0° and 90° and E_p = 150–2500 keV. The results can be explained if a direct radiative capture process, E1(s and d → p), to the ground state in ¹³N is included in the analysis in addition to the two well-known resonances in this beam energy range $\text{[E}{}_{\mathrm{p}}\text{= 457(}\text{1}\text{2}{}^{\mathrm{+}}\text{)}$ and 1699 $\text{(}\text{3}\text{2}{}^{\mathrm{?}}\text{) keV]}$. The direct capture component is enhanced through interference effects with the two resonance amplitudes. From the observed direct capture cross section, a spectroscopic factor of C²S(l = 1) = 0.49 ± 0.15 has been deduced for the $\text{1}\text{2}{}^{\mathrm{?}}$ ground state in ¹³N. Excitation functions for the reaction ${}^{12}\text{C(p,γ}{}_1\text{p}{}^1\text{)}{}^{12}\text{C}$ have been obtained at θ_γ = 0° and 90° and E_p = 610–2700 keV. Away from the 1699 keV resonance the capture γ-ray yield is dominated by the direct capture process E1 (p → s) to the $\text{2366 (}\text{1}\text{2}{}^{\mathrm{+}}\text{) keV}$ unbound state. Above E_p = 1 MeV, the observed excitation functions are well reproduced by the direct capture theory to unbound states (bremsstrahlung theory). Below E_p = 1 MeV, i.e., E_p → 457 keV, the theory diverges in contrast to observation. This discrepancy is well known in bremsstrahlung theory as the “infrared problem”. From the observed direct capture cross sections at $\text{E}{}_{\mathrm{p}}\text{? 1 MeV}$, a spectroscopic factor of C²S(l = 0) = 1.02 ± 0.15 has been found for the $\text{2366 (}\text{1}\text{2}{}^{\mathrm{+}}\text{) keV}$ unbound state. A search for direct capture transitions to the $\text{3512 (}\text{3}\text{2}{}^{\mathrm{?}}\text{)}$and $\text{3547 (}\text{5}\text{2}{}^{\mathrm{+}}\text{) keV}$ unbound states resulted in upper limits of C²S(l = 1) ≦ 0.5 and C²S(l = 2) ? 1.0, respectively. The results are compared with available stripping data as well as shell-model calculations. The astrophysical aspect of the ¹²C(p, γ₀)¹³N reaction also is discussed.     

Radiative lifetimes in MoI using a novel atomic beam source

Radiative lifetimes of the 4d⁵ (a⁶S)5pz ⁷P^o levels and the 4d⁵ (a⁶S)5pz⁵P^o levels in MoI are reported as follows: $\text{τ(}\text{z}{}^7\text{P}{}_4{}^{\mathrm{<mtext>O</mtext>}}\text{) = 15.9}\text{ns}$, $\text{τ(}\text{z}{}^7\text{P}{}_3{}^{\mathrm{<mtext>O</mtext>}}\text{) = 17.0}\text{ns}$, $\text{τ(}\text{z}{}^7\text{P}{}_2{}^{\mathrm{<mtext>O</mtext>}}\text{) = 17.1}\text{ns}$, $\text{τ(}\text{z}{}^5\text{P}{}_3{}^{\mathrm{<mtext>O</mtext>}}\text{) = 22.3}\text{ns}$, $\text{τ(}\text{z}{}^5\text{P}{}_2{}^{\mathrm{<mtext>O</mtext>}}\text{) = 22.1}\text{ns}$, and $\text{τ(}\text{z}{}^5\text{P}{}_1{}^{\mathrm{<mtext>O</mtext>}}\text{) = 21.7}\text{ns}$ (±5%). The lifetimes are measured using time resolved laser induced fluorescence and a novel atomic beam source. This novel hollow cathode effusive beam source produces an intense beam of ground state Mo atoms and metastable Mo atoms. Our measurements on the z ⁷P^O levels are in agreement with earlier lifetime measurements. Our measurements on the z ⁵P^O levels are the first direct radiative lifetime measurements of these levels; the z ⁵P^O measurements are of particular interest because the a⁵S → z⁵P^O multiplet is used to determine the solar abundance of Mo.     

Lifetime and g-factor results for the 132− 1985 keV level in 91Nb and the 152− 2288 keV level in 91Zr

Lifetime and g-factor measurements have been made with pulsed beam-γ time-differential techniques using the ⁸⁹Y(α, 2n)⁹¹Nb and ⁸⁸Sr(α, n)⁹¹Zr reactions. A mean lifetime τ = 14.4 ± 0.5 nsec and a g-factor of 1.26 ± 0.04 were obtained for the $\text{13}\text{2}{}^{\mathrm{?}}$ 1985 keV level in ⁹¹Nb and τ = 41.9 ± 1.2 nsec and g = 0.70 ± 0.01 were obtained for the $\text{15}\text{2}{}^{\mathrm{?}}$ 2288 keV level in ⁹¹Zr. These results are compared to theoretical calculations for $\text{(π}\text{g}{}_{\mathrm{<mtext>9</mtext><mtext>2</mtext>}}\text{)}{}^2\text{(π}\text{p}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{)}$ and $\text{(π}\text{g}{}_{\mathrm{<mtext>9</mtext><mtext>2</mtext>}}\text{)(π}\text{p}\text{1}\text{2}\text{)(v}\text{d}{}_{\mathrm{<mtext>5</mtext><mtext>2</mtext>}}\text{)}$ configurations in ⁹¹Nb and ⁹¹Zr, respectively.     

Negative-parity states in Pb isotopes: g-factor of the 480 ns,if Jπ = 9− isomer in 200Pb

The g-factor of the 480 ns, 9^? isomer at 2.237 MeV in ²⁰⁰Pb was measured by the time-differential perturbed angular distribution method. The result, g = ?0.0285±0.0011 confirms the rather pure $\text{(}\text{f}{}_{\mathrm{<mtext>5</mtext><mtext>2</mtext>}}{}^{\mathrm{?1}}\text{i}{}_{\mathrm{<mtext>13</mtext><mtext>2</mtext>}}{}^{\mathrm{?1}}\text{)}$ quasiparticle structure of this state. Half-lives of 480±20 ns, 43±3 ns and 42±4 ns have been measured for the 2237 keV 9^?, 2154 keV 7^? states in ²⁰⁰Pb and the 2208 keV state in ²⁰²Pb, respectively; E2 transitions and g-factors of negative-parity states in even, neutron-deficient Pb isotopes are discussed.     

Coupling constants for several light nuclei from a dispersion analysis of nucleon and deuteron scattering amplitudes

A forward dispersion relation cannot be applied to charged particle scattering amplitudes unless the influence of the Coulomb interaction is explicitly considered. Earlier studies have shown how Coulomb effects can be taken into account when direct (s-channel or bound-state) poles are investigated. In this paper we extend the Coulomb modification to include I = 0 exchange (u-channel) processes as well. We then apply a forward dispersion relation to empirical d + α, p + d and n + d elastic scattering amplitudes which contain both direct and exchange poles with and without Coulomb effects. We obtain detailed and model-independent information on the following vertices: ⁶Li-α-d (S- and D-state) ⁴He-d-d, ³He-d-p, ³H-d-n and d-p-n. From the coupling constants we calculate the asymptotic normalization (spectroscopic factors) C²₁ of the corresponding cluster wave functions, which become: $\text{C}{}^2{}_0\text{(}{}^6\text{Li}\text{, α}\text{d}\text{) = 4.62 ± 0.23}$, $\text{C}{}^2{}_2\text{(}{}^6\text{Li}\text{, α}\text{d}\text{) = (1 ± 6) × 10}{}^{\mathrm{?4}}$, C²₀(α, dd) < 2, $\text{C}{}^2{}_0\text{(}{}^3\text{He, dp}\text{) = 3.5 ± 0.4}$, $\text{C}{}^2{}_0\text{(}{}^3\text{H, dn}\text{) = 2.6 ± 0.3}\text{and}\text{C}{}^2{}_0\text{(}\text{d, np}\text{) = 1.66 ± 0.1}$.