Two-phonon resonant Raman scattering at the indirect exciton in silver chloride

Resonant Raman scattering in AgCl is reported for the first time. With excitation in the indirect absorption edge at 1.8K the observed scattering processes involve pairs of momentum-conserving TA(L) and LA(L) phonons with energies of 8.2 meV and 12.9 meV, respectively. The dependence of the scattered intensity on excitation energy suggests that, in contrast to AgBr, intravalley scattering by long wavelength acoustic phonons and intervalley scattering are negligibly small, the main relaxation mechanism of the free exciton being self-trapping. Some enhancement in the 2LO scattering intensity observed is probably due to resonance with the lowest direct exciton.     

Significance of intra-cavity power density in synchronous mode-locking of CW-dye lasers

It is shown that there is a well-defined relation between the intra-cavity power density and the temporal structure of ultrashort light pulses generated by a synchronously pumped cw dye laser. To obtain pulses of good quality with high output power the beam cross-section in the lasing medium must be large, because the best performance is achieved at low power density.     

Random fields in the diluted Ising system Fe1−xMgxCl2

We discuss how random fields (RFs) are generated in uniaxial random antiferromagnets by applied fields and report a systematic specific heat study on the three-dimensional (3-D) system Fe_1?xMg_xCl₂ to demonstrate their effects. The RF crossover exponent ø is determined by measuring the shape of the phase boundary in the TH plane and we obtain ø=1.26 ± 0.10, in agreement with theoretical prediction. Drastic changes in the shape of the specific anomaly are observed. We argue that they are due to the temperature dependence of the random fields.     

On the Majorana equations and the rest mass of neutrinos

As is well known, the law of parity conservation does not hold in weak interactions. This type of asymmetry created a number of theoretical problems which were solved, first of all, by a new understanding of the features of neutrinos and their role in weak interactions. These solutions were based, however, essentially on the handedness (chirality) of neutrinos which is closely related to their vanishing rest mass. The thesis of neutrinos with nonvanishing rest mass, newly considered in the literature, therefore requires a rediscussion of the early arguments concerning the relation between the neutrino theory and some weak interaction essentials. When one does this, as in the present paper, it is noted that neutrinos with rest mass lead to some difficulties, in particular to a violation of T invariance.     

Impact of hyperthermic regional perfusion therapy on cell metabolism of malignant melanoma monitored by 31P MR spectroscopy

For the first time, the influence of hyperthermic regional perfusion therapy on tumor cell metabolism has been monitored by means of 31P MR spectroscopy. Shortly after treatment, a complete depletion of high energy phosphates, a significant increase of inorganic phosphate, phosphomono- and phosphodiester resonances and a decrease of pH have been observed. Healthy muscle tissue showed only minor effects caused by this aggressive therapy. The time course of the transient variation of phosphate metabolite concentrations is explained in the framework of a simple pathophysiological model. The results demonstrate that the imediate effect of chemotherapy on tumor tissue can be detected by 31P MRS before any clinical signs of tumor response are visible.     

Demonstration of a 1/4-cycle phase shift in the radiation-induced oscillatory magnetoresistance in GaAs/AlGaAs devices

We examine the phase and the period of the radiation-induced oscillatory magnetoresistance in GaAs/AlGaAs devices utilizing in situ magnetic field calibration by electron spin resonance of diphenyl-picryl-hydrazal. The results confirm a f-independent 1/4-cycle phase shift with respect to the hf=j variant Planck's over 2pi omega(c) condition for j>/=1, and they also suggest a small ( approximately 2%) reduction in the effective mass ratio, m(*)/m, with respect to the standard value for GaAs/AlGaAs devices.     

Quantized ν = 5/2 state in a two-subband quantum hall system

The evolution of the fractional quantum Hall state at filling 5/2 is studied in density tunable two-dimensional electron systems formed in wide wells in which it is possible to induce a transition from single- to two-subband occupancy. In 80 and 60 nm wells, the quantum Hall state at 5/2 filling of the lowest subband is observed even when the second subband is occupied. In a 50 nm well, the 5/2 state vanishes upon second subband population. We attribute this distinct behavior to the width dependence of the capacitive energy for intersubband charge transfer and of the overlap of the subband probability densities.