Radiative fusion from very symmetric reactions: the giant dipole resonance in the Au nucleus

The spectra of high-energy γ rays emitted by the Giant Dipole Resonance (GDR) built on moderately excited states associated with the evaporation of 0, 1 and 2 nucleons were measured in the ⁹⁰Zr + ⁸⁹Y symmetric fusion reaction. The radiative fusion data suggest statistical emission from the compound nucleus. In addition, the analysis of the high-energy γ-ray spectra associated with the different evaporation channels at the present temperature of 0.7 MeV and spin range 15–20 show a fairly narrow width of 5.0±0.35 MeV. This value is smaller than what would be expected in a nucleus where shell effects do not play a role.     

Analysis of the HOOO torsional potential

Torsional levels of cis and trans HOOO and DOOO, observed previously via infrared action spectroscopy [E. L. Derro, T. D. Sechler, C. Murray, and M. I. Lester, J. Chem. Phys. 128, 244313 (2008)], have been used in conjunction with ab initio theory to obtain a torsional potential energy surface for the hydrotrioxy radical. High level electronic structure calculations based on the equation-of-motion coupled-cluster method for ionized states (EOMIP-CCSD) are utilized to produce a torsional potential. Eigenvalues of the potential are computed by diagonalizing the torsional hamiltonian in a free-rotor basis. Uniform scaling of the theoretical potential by a factor of 1.35 yields vibrational frequencies in good agreement with the experiment, and allows prediction of the barrier height to isomerization of ～340 cm(-1) and relative stability of trans-HOOO with respect to cis-HOOO of ～70 cm(-1). Examination of the optimized nuclear coordinates with respect to the torsional angle, suggests that the central O-O bond length is strongly coupled to the torsion and is important in determining the relative stabilities of the two conformers. The scaled potential is then used to determine the torsional contribution to the partition function for atmospheric modeling of HOOO.