Narrow Results

Four-body calculations with explicitly correlated Gaussian bases are performed for excited states of ⁴He. All the levels below E_x=26 MeV are reproduced reasonably well using realistic potentials. An analysis is made to show how the state becomes a resonance but those having almost the same structure as this state in different spin-isospin channels are not observed as resonances. The calculation of spectroscopic amplitudes, nucleon decay widths, and spin-dipole transition strengths demonstrates that the state and the three lowest-lying negative-parity states with 0^- and 2^- have ³H+p and ³He+n cluster configurations, leading to the interpretation that these negative-parity states are the inversion-doublet partners of the state.

The photodisintegration cross section of ⁴He is calculated using the realistic nucleon-nucleon potential Argonne V18 (AV18) and the three-body force Urbana IX (UIX). Final State interaction is taken into account via the Lorentz Integral Transform method. A comparison with other potential models and with the available experimental data is discussed.