We have measured the hyperfine structure of mutually perturbing rovibrational levels of the 1(b) 3Pi0 and 2(A) 1Sigma+ states of the NaK molecule, using the perturbation-facilitated optical-optical double resonance method with copropagating lasers. The unperturbed 1(b) 3Pi0 levels are split into four hyperfine components by the Fermi contact interaction bFIS. Mixing between the 1(b) 3Pi0 and 2(A) 1Sigma+ levels imparts hyperfine structure to the nominally singlet component of the perturbed levels and reduces the hyperfine splitting of the nominally triplet component. Theoretical analysis relates these observations to the hyperfine splitting that each 1(b) 3Pi0 level would have if it were not perturbed by a 2(A) 1Sigma+ level. Using this analysis, we demonstrate that significant hyperfine splitting arises because the 1(b) 3Pi0 state cannot be described as pure Hund's case (a). We determine bF for the 1(b) 3Pi0 levels and also a more accurate value for the magnitude of the singlet-triplet spin-orbit coupling HSO=[1(b) 3Pi0(vb,J)(H(SO))2(A) 1Sigma+(vA,J). Using the known spectroscopic constants of the 1(b) 3Pi state, we obtain bF=0.009 89+/-0.000 27 cm(-1). The values of (H(SO)) are found to be between 2 and 3 cm(-1), depending on vb, vA, and J. Dividing (H(SO)) by calculated vibrational overlap integrals, and taking account of the 1(b) 3Pi(Omega) rotational mixing, we can determine the magnitude of the electronic part H(el) of H(SO). Our results yield (H(el))=(16.33+/-0.15) cm(-1), consistent with our previous determinations using different techniques.

We develop a model that predicts the potential energy function W(R) of a spherical fullerene, CN, near a graphite surface. R is the distance between the fullerene center of mass and the surface. The model is based on summing all the interactions between the C atoms in the fullerene and those on a graphite sheet. The atom-atom potential employed is a Lennard-Jones 12-6 potential with parameters chosen from previous treatments of graphite and of c6O(s). The binding energy is suprisingly large, varying between 15 and 19 kcal/mol for C60 depending on the potential, and scales approximately as N'/*. W(R) is used to determine the force constant and fundamental frequency, as well as the Arrhenius expression A exp(-E,/kT), for desorption d the CN from the graphite surface. This information can be used to determine relative desorption rates as a function of temperature for fullerenes that are more round than cylindrical. We describe and predict the results of a feasible experiment that would measure the temperature-programmed desorption of fullerenes from a graphite surface.

Kinetics following addition of sulfur fluorides to a weakly ionized plasma from 300 to 500 K: Rate constants and product determinations for ion-ion mutual neutralization and thermal electron attachment to SF5, SF3, and SF2 A complex potential model is used to treat the mutual neutralization of positive and negative ions. The model is used to examine neutralization by the charge transfer mechanism and also by internal excitation leading to capture. It is found that electron transfer is the dominant process for simple ions and small hydrated ions. The numerical results of the theory have been parameterized in terms of the reduced mass of the collision and the electron affinity of the electron donor. This procedure yields an approximate scaling formula that fits a wide range of experimental data to an accuracy of about ± 30%.

A quantitative theoretical study of the dissociative recombination of SH with electrons has been carried out. Multireference, configuration interaction calculations were used to determine accurate potential energy curves for SH and SH. The block diagonalization method was used to disentangle strongly interacting SH valence and Rydberg states and to construct a diabatic Hamiltonian whose diagonal matrix elements provide the diabatic potential energy curves. The off-diagonal elements are related to the electronic valence-Rydberg couplings. Cross sections and rate coefficients for the dissociative recombination reaction were calculated with a stepwise version of the multichannel quantum defect theory, using the molecular data provided by the block diagonalization method. The calculated rates are compared with the most recent measurements performed on the ion Test Storage Ring (TSR) in Heidelberg, Germany.