A Mass Formula from Light to Hypernuclei

Simultaneous description of ordinary and hypernuclei masses by a single mass formula has been a great challenge in nuclear physics. Hyperon-separation energies of about forty Lambda($\Lambda$), three Lambda-Lambda($\Lambda\Lambda$), one Sigma($\Sigma$) and seven Cascade($\Xi$) hypernuclei have been experimentally found. Many of these nuclei are of light masses. We prescribe a new mass formula, called BWMH, which describes the normal and hypernuclei on the same footing. It is based on the modified-Bethe-Weizs\"acker mass formula (BWM). BWM is basically an extension of the Bethe-Weizs\"acker mass formula (BW) for light nuclei. The parameters of BWM were optimized by fitting about 3000 normal nuclei available recently. The original Bethe-Weizs\"acker mass formula (BW) was designed for medium and heavy mass nuclei and it fails for light nuclei. Two earlier works on hypernuclei based on this BW show some limitations. The BWMH gives improved agreement with the experimental data for the line of stability, one-neutron separation energy versus neutron number spectra of normal nuclei, and the hyperon-separation energies from hypernuclei. The drip lines are modified for addition of a $\Lambda$ hyperon in a normal nucleus.Comment: Presented at the "XXIX Mazurian Lakes Conference on Physics: Nuclear Physics and the Fundamental Processes, Piaski, Poland, August 30 - September 6, 2005." (7 pages, 1 Table, 1 Figure

Isobaric incompressibility of the isospin asymmetric nuclear matter

The isospin dependence of the saturation properties of asymmetric nuclear matter, particularly the incompressibility $K_\infty (X) = K_\infty + K_\tau X^2 + O(X^4)$ at saturation density is systematically studied using density dependent M3Y interaction. The $K_\tau$ characterizes the isospin dependence of the incompressibility at saturation density $\rho_0$. The approximate expression $K_{asy} \approx K_{sym}-6L$ is often used for $K_\tau$ where $L$ and $K_{sym}$ represent, respectively, the slope and curvature parameters of the symmetry energy at $\rho_0$. It can be expressed accurately as $K_\tau=K_{sym}-6L-\frac{Q_0}{K_\infty}L$ where $Q_0$ is the third-order derivative parameter of symmetric nuclear matter at $\rho_0$. The results of this addendum to Phys. Rev. C 80, 011305(R) (2009) indicate that the $Q_0$ contribution to $K_\tau$ is not insignificant.Comment: 4 pages including 1 table and 1 figur

Alpha decay half-lives of new superheavy elements

The lifetimes of $\alpha$ decays of the recently produced isotopes of the elements 112, 114, 116 and the element $^{294}118$ and of some decay products have been calculated theoretically within the WKB approximation using microscopic $\alpha$-nucleus interaction potentials. These nuclear potentials have been obtained by folding the densities of the $\alpha$ and the daughter nuclei with the M3Y effective interaction, supplemented by a zero-range pseudo-potential for exchange along with the density dependence. Spherical charge distributions have been used for calculating the Coulomb interaction potentials. These calculations provide reasonable estimates for the observed $\alpha$ decay lifetimes and thus provide reliable predictions for other superheavies.Comment: 7 page

Indigenous development of ultra high vacuum (UHV) magnetron sputtering system for the preparation of Permalloy magnetic thin films

We have designed and developed an indigenous ultra high vacuum (UHV) sputtering system which can deposit magnetic thin films with high purity and good uniformity. The equipment consists of state-of the-art technologies and sophistication. With this system it is possible to deposit coatings of various materials on a sample size of 3”3” 3”. The Ni81Fe19 ferromagnetic thin films, with Tantalum (Ta) as a buffer and cap layers have been deposited on silicon substrates using this ultra high vacuum (UHV) sputtering system. The magneto transport measurement study indicated a significant variation in the AMR values of the films for varying thicknesses of tantalum and NiFe layers

Lambda hyperonic effect on the normal driplines

A generalized mass formula is used to calculate the neutron and proton drip lines of normal and lambda hypernuclei treating non-strange and strange nuclei on the same footing. Calculations suggest existence of several bound hypernuclei whose normal cores are unbound. Addition of Lambda or, Lambda-Lambda hyperon(s) to a normal nucleus is found to cause shifts of the neutron and proton driplines from their conventional limits.Comment: 6 pages, 4 tables, 0 figur