Accurate Three-Nucleon Bound-State Calculation with an Extended Separable Expansion of the Two-Body T-Matrix

An accurate solution for the three-nucleon bound state is obtained within 1 keV in the binding energy and, on the whole, better than 1% in the wave function, using a new systematic and efficient method. The method is based on a recently developed separable expansion for any finite-range interaction, in which a rigorous separable series for the two-body t-matrix is obtained by expanding the wave function in terms of a complete set of basis functions inside the range of the potential. In order to treat a potential with a strong repulsive core, as in the case of the Argonne potential, we develop a two-potential formalism. The expansion starts with a few EST (Ernst, Shakin, and Thaler) terms in order to accelerate the convergence and continues with an orthogonal set of polynomials, avoiding the known difficulties of a pure EST expansion. Thus, several techniques are combined in the present extended separable expansion (ESE). In this way, the method opens a new systematic treatment for accurate few-body calculations resulting in a dramatic reduction in the CPU time required to solve few-body equations. Received November 6, 1996; revised April 14, 1997; accepted for publication April 30, 1997     

Enhancing high-order above-threshold dissociation of H2+ beams with few-cycle laser pulses

High-order (three-photon or more) above-threshold dissociation (ATD) of H(2)(+) has generally not been observed using 800 nm light. We demonstrate a strong enhancement of its probability using intense 7 fs laser pulses interacting with beams of H(2)(+), HD(+), and D(2)(+) ions. The mechanism invokes a dynamic control of the dissociation pathway. These measurements are supported by theory that additionally reveals, for the first time, an unexpectedly large contribution to ATD from highly excited electronic states.     

L-S coupling and the magnetic moment of6Li from three-body models

Recently, the shell structure of⁶Li was calculated from three-body models (pn) where the only input is the required nucleon-nucleon and alpha-nucleon interactions. There it was learned, within the framework ofj-j coupling for the two valence nucleons with their coordinate's origin on the alpha particle, that orbitals beyond thep-shell, e.g. thes-d shell, play a significant role in the structure of⁶Li. In the present work, we extend these calculations to thef-shell. Thef-shell orbital probabilities add 4% to the normalization, thus bring all the models to within 3–5% of complete convergence. We then use thej-j coupling orbital amplitudes up to thef-shell to construct the corresponding amplitudes forL-S coupling. We find theL-S orbital probabilities, and compare them with theL-S component probabilities calculated directly by recoupling the three-body wave function from its natural Jacobi-coordinate form. The⁶Li magnetic moment is determined from the directL-S probabilities. The most realistic models yield magnetic moments about 2.5% higher than experiment.