High-frequency breakdown and paschen law

In the present paper an attempt has been made to draw theoretically a correlation between the well-known Paschen curve and the high-frequency breakdown characteristic of a gas device by interpreting electron mean free path in terms of the frequency of the applied field. The analytical high-frequency breakdown characteristic, so obtained, agree fairly well with the experimental results.     

Low-loss rotator and application for isolator design

The Faraday rotation associated with the Zeeman effect in gases is used to rotate the plane or polarization of plane polarized light with low loss of intensity. Advantage is taken of the rapid decrease of absorption relative to Faraday rotation between the split Zeeman components. Calculations of this Faraday rotation are applied to obtain design parameters for an isolator for 5.26 μm which show a significant improvement over conventional designs.     

Thermoelectric power in superlattices of nonparabolic semiconductors with graded interfaces under magnetic quantization

Summary We study the thermoelectric power of the electrons under magnetic quantization in III–V, II–VI, PbTe/PbSnTe and strained layer superlattices with graded interfaces and compare the same with the corresponding bulk specimens of the constituent materials by formulating the respective expressions incorporating the broadening. It is found, by taking GaAs/Ga_1−x Al _x As, CdS/CdTe, PbTe/PbSnTe and InAs/GaSb superlattices with graded interfaces as examples, that the thermoelectric power exhibits oscillatory dependence with the inverse quantizing magnetic field due to Shubnikov-de Hass effect and increases with decreasing electron concentration in an oscillatory manner in all the aforementioned cases. The thermopower in graded superlattices is greater than that of constituent bulk materials together with the fact that the oscillations in superlattices show up much more significantly as compared to the respective constituent materials. In addition, the well-known expressions for bulk specimens of wide-gap semiconductors have also been obtained as special cases from our generalized expressions under certain limiting conditions.     

Bethe-Salpeter dynamics for two-photon processes

Recent experimental data on single hadron production by two-photon beams inpetra andpep have provided a unique opportunity for testing specific models of confinement through a study of one of their cleanest predictionsviz the γγ →H amplitudes. Motivated by this new facility, aqcd-oriented Bethe-Salpeter model of harmonic confinement, which has already been found to describe rather well several classes of hadronic data (from mass spectra to electromagnetic and pionic couplings), is now employed for a detailed comparison of its predictions onP → γγ andT → γγ couplings with the data. The agreement is quite good for all cases except one (η → γγ). This paper is offered as a “Festschrift” in honour of Dr Raja Ramanna on the occasion of his sixtieth birthday. The subject is theoretical in content but seeks to exploit an entirely new window opened by the latest experimental technology (on two-photon physics). As such it is appropriately dedicated to one of the main architects of nuclear science in India.     

K-shell ionisation cross-sections of Cu,Ge, Mo,Ag and Sn by protons of energy 0.3 to 1.8 MeV

K-shell ionisation cross secions of Cu, Ge, Mo, Ag and Sn in proton impact have been measured systematically in the energy range 0.3 to 1.8 MeV. Thin targets have been used in transmission geometry. Data are compared with the predictions of the PWBA and the PWBA modified to include corrections due to Coulomb retardation of the projectile, increased binding of the target electron during collision and the relativistic nature of theK-shell electrons. The intensity ratiosK _α /K _β have also been obtained as a function of proton energy for all the five elements.     

Carbon-13 spectral studies of some chalcones and flavanones

Carbon-13 signal assignments of 2′,4′-dihydroxychalcone, flemichapparin, pashanone, isodidymocarpin, pedicellin, pedicinin, methylpedicinin, didymocarpin-A and the corresponding quinoflavanone dehydrodidymocarpin-A are reported.