S. C. Pancholi

Half-life measurements in59Co,141Pr and227Ac

AbstractThe half-lives of the 1291.6 keV level in59Co, 145.43 keV level in141Pr and 27.35 keV level in227Ac have been measured using leading edge and zero-crossover timing techniques. The decay curves analysed by moments, Laplace transform and slope methods gave the following half-life values:

High-Spin States in Odd–Odd 168Lu

\begin{gathered} T_{\tfrac{1}{2}} (1291.6 keV level in {}^{59}Co) = (0.538 \pm 0.004) ns \hfill \\ T_{\tfrac{1}{2}} (145.43 keV level in {}^{141}\Pr ) = (1.82 \pm 0.04) ns \hfill \\ T_{\tfrac{1}{2}} (27.35 keV level in {}^{227}Ac) = (41.0 \pm 1.1) ns. \hfill \\ \end{gathered}

Shape evolution at high spin states in Kr and Br isotopes

From the measured half-lives, the reduced transition probabilitiesB(M1)↓,B(E2)↓ for gamma transitions de-exciting the above mentioned levels in59Co and141Pr are determined and compared with single particle, intermediate coupling and Sorensen estimates. In227Ac, absolute transition probability for the 27.35 keV transition is determined and compared with single particle and Nilsson estimates.

Band Structure of 85Sr

Abstract A systematic experimental study on sub-nanosecond timing with fast plastic scintillation detectors has been carried out utilizing the leading edge and the constant fraction timing modes. Best time resolution fwhm of 155 ps with a slope of 18 ps has been achieved at 60 Co 1040 keV Compton energy (energy windows 20%) using 1.25 cm ∅ × 0.2 cm NE111 scintillators coupled to XP1021 photomultiplier tubes. A comparative study of XP1021 and RCA8575 tubes yielded best timing fractions of ∼0.10 and ∼0.20 respectively. Reduction of the utilized photocathode area by one-quarter improves the time resolution marginally for these tubes. A comparison of the timing performance of NE102A. Pilot B and NE111 scintillators shows that the time resolution is worse by ∼20% and ∼8% respectively for NE102A and Pilot B as compared to that for NE111. The effect of scintillator height on the time spread of light collection from the NE111 scintillators has been studied. It is observed that the time resolution improves considerably with a large decrease in the scintillator height and the resulting improvement is different for different incident photon energies. In addition, a few other timing studies have also been made and these are described in the text.

High spin states in {sup 139}Pm

Abstract: High-spin states in the odd-odd 168Lu nucleus, populated in the 154Sm(19F,5n) reaction at a beam energy of 96 MeV, were investigated using in-beam γ-ray spectroscopy techniques. The BC neutron crossing in the yrast band, based on πg7/2[404]7/2+⊗νi13/2[642]5/2+ configuration, occurs at ħω= 0.31 MeV. The two side bands, based on πh11/2[514]9/2−⊗νi13/2[642]5/2+ and πh9/2[541]1/2−⊗νi13/2[642]5/2+ configurations, show anomalous signature-splitting and signature-inversion in the first one, to occur at ħω= 0.24 MeV. A moderately delayed BC-crossing is anticipated in the second one.

Shape evolution of the highly deformed {sup 75}Kr nucleus examined with the Doppler-shift attenuation method

The internal conversion coefficients have been measured using a high resolution low energy Ge(Li) detector for the followingM4 transitions:125Te: 109.27keV transitionαT=357±11; RG method,127Te: 88.26 keV transitionαT=484±23; XPG method,129Te: 105.50keV transitionαT=213±10; XPG method.It is observed that these values are lower by 2.5–3.6% as compared with Hager and Seltzers calculations. A comparison between experimental and theoreticalαT andαT values for elevenM4 transitions shows that the experimental values are systematically lower.

HIGH SPIN STATES IN 139Pm

The high spin states in A = 75, Kr and Br isotopes have been populated via fusion-evaporation reaction at an incident beam energy of 90 MeV. The de-exciting γ-rays were detected utilizing the Indian National Gamma Array (INGA). Lifetime of these excited high spin states were determined by Doppler-shift attenuation method. Experimental results obtained from lifetime measurement are interpreted in the frame work of projected shell-model to get better insight into the evolution of collectivity. Comparison of the calculations of the model with transitional quadrupole moments Qt of the positive and negative parity bands firmly established their configurations.

Multiple antimagnetic rotation bands in odd-A107Cd

High spin states in 85Sr were populated using the reaction 76Ge(13C, 4n) at a beam energy of 52 MeV. Gamma‐gamma coincidence measurements along with investigation of directional correlation ratios were utilized to establish the extended level scheme upto Iπ = (35/2−). One of the positive parity states observed at 3383.3 keV ((Iπ = 19/2(+)) may be considered as a magnetic rotational (ΔI = 1) band, the negative parity states built on 3028.0 level show an irregular behaviour and does not exhibit magnetic rotation.