Control of high-order harmonics from H2+ and D2+ for producing intense single attosecond pulse

Generally, the intensities of molecular high-order harmonic spectra from [Formula: see text] and its isotope molecules are quite different due to the effect of nuclear signals. Thus, in this paper, we investigate the change law of harmonic spectra from [Formula: see text] and [Formula: see text] driven by different laser fields and try to find the optimal harmonic spectra for producing intense single attosecond pulses (SAPs). The results show that in lower laser intensity case, the harmonic yield follows as [Formula: see text]; while, in higher laser intensity case, the harmonic yield meets the condition of [Formula: see text]. Further, by using this change law of harmonic yield and choosing the optimal harmonic emission peak (HEP), we can obtain the intense spectral continuum with the assistance of the half-cycle pulse (HCP). Next, with the superposition of some harmonics on the spectral continuum, the intense SAPs shorter than 37 as can be obtained from [Formula: see text] and [Formula: see text] harmonic spectra. Finally, the results show that the stronger attosecond signals can be obtained when the light nucleus or heavy nucleus molecules are driven by lower or higher laser intensities, respectively.

Description of the Fission Process: Nuclear Models for Fission Dynamics

Nuclear fission is the splitting of a heavy nucleus into two or more fragments, a process that releases a substantial amount of energy. It is ubiquitous in modern applications, critical for national security, energy generation and reactor safeguards. Fission also plays an important role in understanding the astrophysical formation of elements in the universe. Eighty years after the discovery of the fission process, its theoretical understanding from first principles remains a great challenge. In this paper, we present promising new approaches to make more accurate predictions of fission observables.

Multipole expansion of densities in the deformed relativistic Hartree–Bogoliubov theory in continuum

The deformed relativistic Hartree–Bogoliubov theory in continuum (DRHBc) has been proved as one of the best models to probe the exotic structures in deformed nuclei. In DRHBc, the potentials and densities are expressed in terms of the multipole expansion with Legendre polynomials, the dependence on which has only been touched for light nuclei so far. In this paper, taking a light nucleus [Formula: see text]Ne and a heavy nucleus [Formula: see text]U as examples, we investigated the dependence on the multipole expansion of the potentials and densities in DRHBc. It is shown that the total energy converges well with the expansion truncation both in the absence of and presence of the pairing correlation, either in the ground state or at a constrained quadrupole deformation. It is found that to reach the same accuracy of the total energy, even to the same relative accuracy by percent, a larger truncation is required by a heavy nucleus than a light one. The dependence of the total energy on the truncation increases with deformation. By decompositions of the neutron density distribution, it is shown that a higher-order component has a smaller contribution. With the increase of deformation, the high-order components get larger, while at the same deformation, the high-order components of a heavy nucleus play a more important role than that of a light one.