Electronic structure and hyperfine interaction of muonium in semi-conductors

The Unrestricted Hartree-Fock self-consistent field cluster procedure is being utilized for first-principle investigations of the electronic structures and hyperfine interactions in normal and anomalous muonium states in semi-conductors. Our results for the total energy for the normal muonium state for a twenty-seven atom cluster in diamond, including the muonium and its neighboring atoms, show a minimum at the tetrahedral site and a maximum at the hexagonal site indicating that normal muonium is located in the tetrahedral region and avoids the hexagonal region. Using the calculated spin-density as a function of the position of muonium and carrying out averaging over the vibrational motion of the muon governed by the total energy curve obtained from our work, we have derived a muon hyperfine constant which is about 75% of that in free muonium, in good agreement with experiment. The natures of the total energy and spindensity curves permit us to draw conclusions regarding the origin of the observed trend in the hyperfine constants for normal muonium in diamond, silicon and germanium. The UHF cluster procedure is also applied to study a model of a muon in a positively charged environment for the anomalous muonium center in diamond. This model leads to a hyperfine interaction tensor with the observed feature of strong anisotropy but significantly weaker than experiment. The results obtained for this model indicate the importance for the anomalous muonium state with its relatively weak hyperfine interaction, of exchange polarization effects inherent in the UHF procedure.     

Ab initio studies of a proposed mechanism for N-Nitrosamine formation

The geometry of a proposed intermediate (α-dialkylamino nitrite ester) of N-nitrosamine synthesis from nitrites is studied by ab initio SCF methods. The energy of a zwitterion is calculated and found to be high.     

Ab initio studies of negative ion-molecule(s) clusters present in the atmosphere. III. OH−(CO2)n for n = 1, 2

Clusters formed by the OH^? ion and carbon dioxide are investigated using ab initio Hartree–Fock calculations, with 6–31 G and 6–31 G* basis sets. Geometries and binding energies are determined.     

Demilitarized zone planning: A multiobjective approach

The demilitarized zone has been used frequently as a means to separate conflicting nations. Imposition of a buffer zone free from military activities is considered to be an effective first step to restore peace between hostile nations. The demilitarized zone is usually patrolled by third-party forces to discourage military hostilities. This paper deals with the problem of allocating the third-party supervisory forces in order to assure effective policing of demilitarized zones where there are multiple and conflicting objectives.     

New ultra-high resolution dye laser spectrometer utilizing a non-tunable reference resonator

A new dye laser spectrometer utilizing a non-tunable reference resonator is described. The resonator consists of two Zerodur mirrors optically contacted to a Zerodur spacer. Frequency scanning of the laser is provided by acoustooptic modulation. Residual drifts of the resonator frequency — measured on line — are compensated automatically by corresponding corrections of the modulation frequency. The stability during several hours and the resettability of the dye laser frequency are±2.5 kHz and±10 kHz, respectively.