We investigate the excitation spectrum of a singly charged LiF surface using an embedded cluster approach. The spectrum is determined by multiconfiguration self-consistent field calculations. We find stable trionic states, i.e., quasimolecular states of a three-quasiparticle complex consisting of two holes and one electron interacting through the Coulomb potential. The excitation energy of the ...

Quantum beats of heavy and light holes in GaAs quantum wells are investigated in femtosecond time-resolved four-wave mixing and transmission experiments as a function of optical excitation energy. Under nonexcitonic excitation conditions, the four-wave mixing signal disappears due to the immediate loss of the interband coherence of continuum states. In the transmission experiment, the quantum b...

background: ionizing radiation causes deleterious effects on living system mainly due to oxidative damages of macromolecules and protein is the major target due to its abundance. the aim of this study was to investigate the effects of ionizing radiation induced changes in the molecular properties of bovine serum albumin (bsa) its secondary and tertiary structures, degradation, cross linking and...

We investigate the hard nonresonant excitation of the forced Duffing equation with a positive damping parameter E. Using the symbolic manipulation system MACSYMA, a computer algebra system. we derive the two term perturbation expansion by the method of multiple time scales. The resulting approximate solution is valid for small values of the coefficient e As the damping parameter e increases, th...

The suppression of the regenerative chatter phenomenon in turning process via the variation of the frequency and amplitude of the spindle motor excitation is carried out in this research. A programmable inverter is employed for variable periodic excitation of the spindle motor. A set of turning experiments is designed and performed on a number of conical work pieces both in constant spindle spe...

Ion-beam cancer therapy is a promising technique to treat deep-seated tumors; however, for an accurate treatment planning, the energy deposition by the ions must be well known both in soft and hard human tissues. Although the energy loss of ions in water and other organic and biological materials is fairly well known, scarce information is available for the hard tissues (i.e., bone), for which ...

We have determined an upper limit to the kinetic temperature of the gas in the circumstellar envelopes of 2 Be stars, a hot star Cas, and a cooler star 1 Del, by including in an approximate manner the diiuse radiation produced in the envelope. We computed the temperature as a function of position by balancing at each position the rates of energy gain and energy loss. Photoionization, collisiona...