73 research outputs found
Low energy collective modes of deformed superfluid nuclei within the finite amplitude method
Background: The major challenge for nuclear theory is to describe and predict
global properties and collective modes of atomic nuclei. Of particular interest
is the response of the nucleus to a time-dependent external field that impacts
the low-energy multipole and beta-decay strength.
Purpose: We propose a method to compute low-lying collective modes in
deformed nuclei within the finite amplitude method (FAM) based on the
quasiparticle random-phase approximation (QRPA). By using the analytic property
of the response function, we find the QRPA amplitudes by computing the residua
of the FAM amplitudes by means of a contour integration around the QRPA poles
in a complex frequency plane.
Methods: We use the superfluid nuclear density functional theory with Skyrme
energy density functionals, FAM-QRPA approach, and the conventional matrix
formulation of the QRPA (MQRPA).
Results: We demonstrate that the complex-energy FAM-QRPA method reproduces
low-lying collective states obtained within the conventional matrix formulation
of the QRPA theory. Illustrative calculations are performed for the isoscalar
monopole strength in deformed 24Mg and for low-lying K = 0 quadrupole
vibrational modes of deformed Yb and Er isotopes.
Conclusions: The proposed FAM-QRPA approach allows one to efficiently
calculate low-lying collective modes in spherical and deformed nuclei
throughout the entire nuclear landscape, including shape-vibrational
excitations, pairing vibrational modes, and beta-decay rates.Comment: 9 pages, 2 figures, submitted to Phys. Rev.
Asymptotic Behavior of the Wave Packet Propagation through a Barrier: the Green's Function Approach Revisited
To model the decay of a quasibound state we use the modified two-potential
approach introduced by Gurvitz and Kalbermann. This method has proved itself
useful in the past for calculating the decay width and the energy shift of an
isolated quasistationary state. We follow the same approach in order to
propagate the wave-packet in time with the ultimate goal of extracting the
momentum-distribution of emitted particles. The advantage of the method is that
it provides the time-dependent wave function in a simple semi-analytic form. We
intend to apply this method to the modeling of metastable states for which no
direct integration of the time-dependent Schroedinger equation is available
today.Comment: 7 page
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