Nuclear deorientation for heavy ions recoiling in vacuum and low pressure gas

Abstract

Time-differential perturbed gamma-ray angular correlations have been measured for 148'15~ recoiling into vacuum and into helium (v/c= 1.3 ~o) in the pressure region from 0.75 to 25Torr. A model is presented of the perturbation mechanism for recoils travelling in vacuum, which allows for the hitherto hidden fact that a hard core of the attenuation exists. In addition, a higher order modification of the first order Abragam and Pound theory for random perturbations has to be taken into account at very low pressure.

Shape ofAr44: Onset of deformation in neutron-rich nuclei nearCa48Zielińska1, Goergen2, Clément3 et al. 2009Phys. Rev. C2711570View full textAdd to dashboardCite

“…The γ -ray intensities were corrected for internal conversion, and the angular correlation of the γ rays was corrected for relativistic effects and the attenuation caused by the deorientation effect during recoil into vacuum. The latter was caused by the interaction of the recoiling nucleus with the fluctuating hyperfine fields of the atomic electrons, which was treated in a simplifying phenomenological model [31,32].…”

“…While the N = 20 shell closure disappears rather abruptly between 34 Si and 32 Mg, evidence has been accumulated recently for a more gradual erosion of the neutron shell closure in the proton-deficient N = 28 isotones below 48 Ca. The shell closure at N = 28 is the first one driven by the spin-orbit interaction and, unlike N = 20, separates orbitals of the same parity.…”

Shape coexistence in neutron-deficient krypton isotopes

“…The effect attenuates the angular distribution of the γ rays. The complex deorientation effect is treated in a simplifying phenomenological two-state deorientation model [23,24]. The most important parameters in this model are the spin and lifetime of the state, as well as its gyromagnetic factor.…”

First-excited state g factor of Te136 by the recoil in vacuum method

“…As the difference between the inferred g factor for n = 2.2 and n = 2 is negligible, and as there is a precedent for n = 2 in the literature (see e.g. [36][37][38]), n = 2 was adopted for subsequent analysis. The parameters for n = 2 are given in Table III.…”