K. M. Sando

Dirac-Fock discrete-basis calculations on the beryllium atom

Abstract Calculations have been performed on the beryllium atom with basis sets of the type used by Drake and Goldman in calculations on one-electron systems. Energies are found to converge toward the Dirac-Fock limit monotonically from above. A basis introduced by Huzinaga, shown to have properties in common with those of Drake and Goldman, is found to produce similar good results.

Reactive collision dynamics by far wing laser scattering: Mg+H2

We have measured the far wing absorption profiles of the MgH2 collision system leading to both the nonreactive formation of Mg* and into two distinct final rotational states of the reaction product MgH (v‘=0, J‘=6, 23). We have observed qualitatively expected behavior including a pronounced red wing in the reactive absorption profile indicating strong reaction probability on the excited attractive potential surfaces. We have also observed novel aspects of the excited state dynamics including reactive vs nonreactive channel competition effects and a strong far blue wing reactive absorption suggesting significant reaction probability even for trajectories on the repulsive surfaces. We have developed a simple theoretical model to semiquantitatively explain our experimental results. This model uses standard quasistatic theory to estimate the absorption probability as a function of detuning between levels of MgH2 and with assumed nonreactive vs reactive branching ratios, accounts for the subsequent evolution on the excited potential surfaces. This theory correctly predicts the overall shapes of the profiles and in general gives reasonable predictions for the relative magnitudes of the wing intensities.We have measured the far wing absorption profiles of the MgH2 collision system leading to both the nonreactive formation of Mg* and into two distinct final rotational states of the reaction product MgH (v‘=0, J‘=6, 23). We have observed qualitatively expected behavior including a pronounced red wing in the reactive absorption profile indicating strong reaction probability on the excited attractive potential surfaces. We have also observed novel aspects of the excited state dynamics including reactive vs nonreactive channel competition effects and a strong far blue wing reactive absorption suggesting significant reaction probability even for trajectories on the repulsive surfaces. We have developed a simple theoretical model to semiquantitatively explain our experimental results. This model uses standard quasistatic theory to estimate the absorption probability as a function of detuning between levels of MgH2 and with assumed nonreactive vs reactive branching ratios, accounts for the subsequent evolution o...

Molecular dynamics simulation of a fluid of hard spherocylinders

Using the molecular dynamics method we have computed the compressibility factor, orientational order parameter, velocity autocorrelation function, and diffusion constants for a system of 256 hard spherocylinders at two densities in the liquid region. The equation of state is in agreement with that found by the Monte Carlo method and that predicted by the scaled particle theory. The calculated orientational order parameter was near the expected value of (1/N)1/2 for an isotropic system.

Electronic assignments of the violet bands of sodium

Abstract The puzzling violet bands of sodium ( ≈ 425-460 nm), known since 1932, are shown conclusively to arise from the superposition of two distinct continuum emission bands - one singlet (2 1 Σ + u → X 1 Σ + g ) and one triplet (primarily 2 3 Π g → 1 3 Π u + ). Each continuum emission system shows complex interference structure arising from multiple branches of the Mulliken difference potential.

Reactive collision dynamics of Na*(4 2P)+H2 and HD: Experiment and theory

We have used a ‘‘half‐collision’’ pump–probe technique to measure the far wing absorption profiles of the NaH2 collision complex leading to the nonreactive formation of Na* and to four distinct final rotational states of the reaction product NaH(v‘=1, J‘=3, 4, 11, and 13). We have observed reaction on both the attractive potential energy surfaces and over a barrier on the repulsive surface. We have observed the effect of the Na* reagent electronic orbital alignment on the NaH final product rotational state distribution. Specifically, absorption to the repulsive surface leads preferentially to low‐rotational product states, while absorption to the attractive surfaces leads preferentially to high‐rotational product states of NaH. Isotopic substitution experiments give evidence of a kinematic isotope effect on the product rotational state distribution for reactive trajectories on the repulsive surface. We have developed a simple model using a quantum mechanical line shape calculation to estimate the NaH2 abs...

Direct excitation studies of the diffuse bands of alkali metal dimers

Direct dye laser excitations of the K2 yellow, Rb2 orange, and Cs2 near‐infrared diffuse bands have been investigated. Experimental results are shown to be consistent with the assumed bound–free 2 3Πg–1 3∑+u excitations. It is found that for Rb2 and Cs2, spin–orbit interactions become so significant that the 2 3Πg state is strongly split into three quite independent component states.

Features of the energy surface in Dirac-Fock discrete basis description as applied to the Be atom

Abstract The features of the Be atoms energy surface as a function of basis set exponents in the Slater-type basis have been examined for both “balanced” and “unbalanced” basis sets. The results clearly show that the “balanced” basis guarantees a minimum energy which is an upper bound to the numerical Dirac-Fock limit. The “unbalanced” basis, however, gives a minimum energy which is much lower than the numerical limit.

Expansion calculations with the dirac Hamiltonian: 1S12 and 2P12 states of hydrogenic systems

Abstract The method of expansion in a balanced basis has been used for the 1S 1 2 state of Dirac-Coulomb hydrogenic systems using Slater-type basis functions with integer and non-integer powers of r . A single function with integer power of r is shown to give the exact 1S 1 2 energy although the wavefunction is not exact. Application of the balanced basis scheme to the 2P 1 2 state does not always lead to an upper bound to the energy unless both upper and lower components of the exact 2P 1 2 wavefunction have infinite cusps at the origin. Application of the balanced basis expansion of the Drake-Goldman type to 2P 1 2 fails to reproduce the nodal structure although the expansion gives the exact 2P 1 2 energy at a single minimum. We discuss how to avoid such spurious solutions.

Theoretical study of wings of resonance lines of lithium and sodium perturbed by rare gases

A new quantum mechanical method for the evaluation of intensities in the wings of allowed atomic spectral lines is reported. Mathematical and computational comparisons between classical and quantum mechanical methods are made. Wing intensities predicted from three sets of interaction potentials are compared with observed intensities for the red wing of the Li resonance line perturbed by He. Discussions of qualitative features of alkali metal–rare gas potentials and of satellite bands in the wings of the spectral lines of Li and Na perturbed by rare gases are given.

Long-range interaction between metastable helium and ground state helium.

Results of analysis for the long-range interaction between ground state helium and triplet metastable helium, which shows that the long-range coefficient is the same for both gerade and ungerade states. Those terms which lead to the second term on the right hand side of a developed equation vanish through spin selection rules.