A. K. Singh

One- and two-phonon wobbling excitations in triaxial 165Lu

High-spin states in Lu-165 have been investigated by in-beam gamma-ray coincidence spectroscopy using the EUROBALL spectrometer array. Two new excited rotational bands have been discovered with features similar to a previously known triaxial superdeformed band in that nucleus. Comparison of the decay pattern of these bands, in particular the unusually large E2 transition strength from the first excited to the yrast superdeformed band, to theoretical calculations shows that they belong to a family of wobbling excitations with phonon numbers n(w) = 0, 1 and 2. These results, together with evidence for nuclear wobbling in the neighbouring isotopes Lu-163 and Lu-167, firmly establish this mode of excitation in the A = 165 mass region. The observation of wobbling is a unique signature of stable nuclear triaxiality

Small quadrupole deformation for the dipole bands in 112 In

High spin states in 112 In were investigated using the 100 Mo( 16 O ,p 3n) reaction at 80 MeV. The excited level has been observed up to 5.6 MeV excitation energy and spin ∼20¯ h with the level scheme showing three dipole bands. Polarization and lifetime measurements were carried out for the dipole bands. Tilted axis cranking model calculations were performed for different quasiparticle configurations of this doubly odd nucleus. Comparison of the calculations of the model with the B(M1) transition strengths of the positive- and negative-parity bands firmly established their configurations.

Detailed study of magnetic rotation in 196Pb

Abstract High-spin states in 196 Pbxa0have been populated in two different heavy-ion-induced reactions using thin and Au-backed targets, respectively. Gamma-ray coincidences were measured using the EUROBALL spectrometer array. Five new magnetic-rotational bands have been found. The previously known four bands have been extended and some of their levels have been reordered. With one exception, all the bands have been connected to lower-lying states and excitation energies, spins and parities have been determined. From the systematic properties of the bands and from comparison to tilted-axis cranking calculations, arguments for configuration assignments to the bands are derived. It is suggested that the bands are based on proton 11 − and 8 + particle states coupled to various neutron–hole excitations.

Chemical constituents and antioxidant activity of the Arctic mushroom Lycoperdon molle Pers

The biochemical adaptations of fungi to the harsh conditions of the Arctic may mean that these organisms have properties useful to people. Using samples of the puffball mushroom Lycoperdon molle Pers. (Basidiomycota, Fungi) collected at Ny-Ålesund, Svalbard, we examined the in vitro antioxidant potential of this species by investigating its free-radical scavenging (FRS) activity, inhibition of lipid peroxidation (ILP) and Trolox equivalent antioxidant capacity (TEAC). The FRS activity of the samples in various organic solvents, including methanol, ethanol, acetone and dimethyl sulfoxide (DMSO), were found to be in the range of 44.00–89.60%, while ILP activities ranged from 32.00 to 54.41%. The methanol extract showed the highest levels of FRS (89.60%) and ILP (54.41%) compared to standard antioxidants butylated hydroxyanisol and butylated hydroxytoluene (BHT). The TEAC value was also found to be higher compared to the standard water soluble vitamin E analogue Trolox (3.9 mM). Antimicrobial screening of Lycoperdon molle extracts was negative to the tested microorganisms. Using electrospray ionization mass spectrometry (ESI-MS), we determined that the samples contained compounds such as phosphoethanolamine, monomethyl arsenic acid, phosphatidyl glycerol, phosphoionositol, phosphoserine and lysophosphatidyl choline. We found that Lycoperdon molle showed strong antioxidant abilities compared to the standards, suggesting that this and perhaps other Arctic mushrooms could be valuable sources of natural antioxidants for the pharmaceutical industry. To our knowledge, this is the first report of the antioxidant activity in any Arctic mushroom.

Preliminary study of feasibility of an experiment looking for excited state double beta transitions in tin

AbstractA rst attempt to study the feasibility of an experiment to search for doublebeta decay in 124 Sn and 112 Sn was carried out by using ultra-low backgroundHPGe detector (244 cm 3 ) inside the Gran Sasso National Laboratory (LNGS)of the INFN (Italy). A small sample of natural Sn was examined for 2367.5 h.The radioactive contamination of the sample has been estimated. The data hasalso been considered to calculate the present sensitivity for the proposed search;half-life limits ˘10 17 11210 18 years for + EC and EC-EC processes in Sn and˘10 18 years for transition in 124 Sn were measured. In the last sectionof the paper the enhancement of the sensitivity for a proposed experiment withlarger mass to reach theoretically estimated values of half-lives is discussed.Keywords: Double beta decay, ultra low background, HPGe detector1. IntroductionThe existence of non-zero mass of neutrino has been established by neutrinoavor-oscillation experiments [1{3]. However, the nature of the neutrino, eitherDirac or Majorana, can only be tested through observation of neutrino-less

High-spin spectroscopy of 140Nd

The population of the high-spin states in Nd-140 was investigated using the reaction Zr-96(Ca-48,4n). The results from two experiments, one with the EUROBALL array and one with the JUROGAM II + RITU + GREAT setup employing the recoil decay tagging technique, have been combined to develop a very detailed level scheme for Nd-140. Twelve bands of quadrupole transitions and eleven bands of dipole transitions were identified and their connections to low-lying states were established. Calculations using the cranked Nilsson-Strutinsky and the tilted axis cranking models were used to interpret the observed structures. The overall good agreement between the experimental results and the calculations assuming a triaxial shape of the nucleus strongly support the existence of a stable triaxial shape at high spins in this mass region. (Less)

Energy levels in 141Nd from fusion evaporation study

The nucleus 141Nd has been investigated using two different heavy ion fusion evaporation reactions, namely 130Te(16O, 5n) at Elab = 80–85 MeV and 124Sn(24Mg,α3n) at Elab = 107 MeV, and the de-exciting gamma rays were detected using HPGe(GDA) and Clover detector (INGA) arrays, respectively. More than 30 new gamma transitions have been placed in the proposed level scheme, which has been extended up to 9 MeV excitation energy and spin parity values of 45/2−. Spin parity assignments have been made to most of the newly proposed levels. The structure up to approximately 6 MeV excitation energy and spin 31/2− can be explained using the shell model in a truncated basis. The levels with higher spin/energy cannot be described using even the full 50–82 shell, indicating the influence of neutron excitations across the shell gap in this mass region. One M1 band that has been observed is proposed to have a five quasiparticle configuration.

Rotational band in111Sn

Partial level scheme of the neutron deficient111Sn isotope is established upto an excitation energy of about 9 MeV and Iπ=43/2− from γ-rays following103Rh(12C, p3n) reaction. Clear evidence for the existence of a negative parity rotational band aboveγ=23/2−, most probably based on 3p-2h configuration, is obtained.

Antimagnetic rotation and sudden change of electric quadrupole transition strength in 143Eu

Abstract Lifetimes of the states in the quadrupole structure in 143 Eu have been measured using the Doppler shift attenuation method and the parity of the states in the sequence has been firmly identified from polarization measurements using the Indian National Gamma Array. The decreasing trends of the deduced quadrupole transition strength B ( E 2 ) with spin, along with increasing J ( 2 ) / B ( E 2 ) values before the band crossing, conclusively establish the origin of these states as arising from antimagnetic rotation. The abrupt increase in the B ( E 2 ) values after the band crossing in the quadrupole band, a novel feature observed in the present experiment, may possibly indicate the crossing of different shears configurations resulting in the re-opening of a shears structure. The results are reproduced well by numerical calculations within the framework of a semi-classical geometric model.

Structure of Dipole Bands in 112In: Through Lifetime Measurement

High-spin states of the 112In nucleus have been populated via 100Mo(16O, p3n) reaction at 80 MeV beam energy. Lifetimes of excited states of dipole bands have been measured using Doppler-shift attenuation method. The B(M1) transition rates deduced from the measured lifetimes show a rapid decrease with increasing angular momentum. The decrease in B(M1) values are well accounted by the prediction of tilted axis cranking calculations. These measurements confirm the presence of shears mechanism in this nuclei.