Semiempirical molecular orbital calculations for four-, six- and eight-atom systems

The geometry, bond order, binding energy, ionisation potential, dipole moment and net charges have been calculated for cis-N₂O₂, trans-N₂O₂, N₂O₄, BF₃, CH₃, NH₃, BH₃ and B₂H₆ systems using semiempirical molecular orbital methodsindo and the results compared with available experimental,ab initio andmindo/3 data.     

Exact energy eigenvalues by summation of thejwkb series

For the potentialV(x)=V ₀ tan² x, the corrections to the lowest orderjwkb (Bohr-Sommerfeld) energy quantization rule are non-zero. These higher order corrections are explicitly computed using the formalism of Dunham. The resultingjwkb series for the energy eigenvalues is summable, and yields the exact bound state spectrum.     

A programmable digital pulse generator for pulsednmr spectroscopy

The pulse programmer generates highly stable pulses and is capable of producing various scheme of pulses (i.e. a given specific number of pulses with independently variable widths and separations) employed in pulsednmr spectroscopy. The construction and working of the programmer is described with reference to the two most commonly used schemes, namely, a two-pulse sequence and the Carr-Purcell sequence.     

Angular distribution in ternary fission

The angular distribution of long-range alpha particles emitted in keV-neutron induced fission of²³⁵U has been measured using a technique which employs only a particle telescope to derive the angular information. The neutron energy region investigated is 100 keV-1 MeV. The angular distribution oflras has been found to be peaked perpendicular to the neutron-direction with a substantial amount of anisotropy near 200 keV.     

Change of confinement scale in nuclei and the EMC effect

We study a model in which the confinement scale of quarks in a nucleus of massA changes asA ^1/3. This explains theA dependence of structure functions (emc effect) as seen in muon, electron and antineutrino deep inelastic scattering from nuclear targets. We also investigate a prediction of this model—anA dependence of theqcd scale parameter A.     

EXAFS study of intermetallics of the type RGe2 (R=La,Ce, Pr,Nd, Sm,Gd, Tb,Dy, Ho,Er and Y) Part II: Determination of Ge-R distances

The extended x-ray absorption fine structure (EXAFS) associated with the GeK x-ray absorption discontinuity in pure germanium and in the intermetallics RGe₂ (R=La, Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er and Y) has been studied. The Ge-R distances in these compounds have been determined by comparing the experimental phase shifts with the theoretical ones. The Ge-R distances in the compounds TbGe₂, HoGe₂ and ErGe₂ are being reported for the first time in this work.     

EXAFS study of intermetallics of the type RGe2 (R=La,Ce, Pr,Nd, Sm,Gd, Tb,Dy, Ho,Er and Y) Part I: Determination of Ge-Ge distances

A study of theEXAFS associated with theK x-ray absorption discontinuity of germanium in pure germanium and in the rare-earth germanides RGe₂ (where R=La, Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er and Y) has been carried out. The Ge-Ge distances have been obtained in these compounds. Considering the phase to the RGe₂ system, the bond lengths in these compounds have been determined. The values obtained by us for the RGe₂ compounds (R=La, Ce, Pr, Nd, Sm, Gd, Dy and Y) agree with those obtained earlier by crystallographic methods. The bond lengths for the compounds TbGe₂, HoGe₂ and ErGe₂ are also being reported.     

deSitter space-time and rotation

A metric containing a parameterb is presented. It represents two distinct families of space-times, the Taub-nut family and the deSitter family, according asb=1 andb=4 respectively. The metric of the deSitter family of space-times contains a further parameterm. Whenm=0, the space-time is the usual homogeneous and isotropic deSitter space-time. But ifm≠0, the metric represents a space-time which is homogeneous but not isotropic satisfyingR _ik =Λg _ik . In this space-time, the 4-velocity of an observer at rest will have non-zero twist. The metric withb=4,m≠0 is interpreted as a metric representing a “rotating deSitter space-time”.     

The application ofclean to crystallographic problems

It is suggested that the radio astronomical technique of image reconstruction calledclean could be profitably used in crystallography to improve sharpened Patterson maps andE-maps. The method is here generalized to handle the symmetries which arise in crystallographic maps. Simulations on model one and two dimensional structure are presented to illustrate the power of the method.     

Electrical and photoelectrical studies of plasma polymerized acrylonitrile

The electrical and photoelectrical properties of plasma polymerized acrylonitrile (PAN) are reported. The polymer films were studied in silver-PAN-silver systems. Electrical conductivity at room temperature was of the order of 10⁻¹¹ ohm⁻¹ cm⁻¹. The space charge limited current (SCLC) studies at room temperature and thermally stimulated current studies (TSC) over a temperature range of 290–500°K led to a clear understanding of carrier concentration, carrier mobility, trapping levels and activation energies. Photoelectric measurements were used to draw a band picture in plasma depositedPAN.     

Inner shell structure of heavy atoms

The inner-shell structure of some heavy atoms is examined using a self-consistent relativistic local density method. Ar(K), Kr(K) and Xe (K,L ₁,L ₂ andL ₃) binding energies and {ie863-1} (hyper-satellite) energies of Tl, Hg and Tm are calculated. The results are compared with available experimental data. A part of this work was presented byMPD at the Trieste International Symposium on “Core level excitations in atoms, molecules and solids,” 22–26 June 1981, Extended Abstracts (ed.) E Tosatti, ICTP Report No. 89/81 p. 11.     

Study ofl-tryptophan corepressor binding to mutatedE. coli tryptophan repressor proteins by optically detected triplet-state magnetic resonance

Phosphorescence and optically detected magnetic resonance (ODMR) measurements have been carried out on the tryptophan (Trp) residues ofEscherichia coli Trp repressor protein (W Rep) and its two single Trp-containing mutants, W19F and W99F. The enhanced resolution afforded by the W19F and W99F mutants allowed us to characterize the triplet state of boundl-Trp corepressor using phosphorescence wavelengt-selected ORMR spectroscopy. We find that at 77 K the 0,0 band peak wavelength ofl-Trp is shifted from 405.5 nm in the aqueous solvent to ca. 410 nm when bound to the corepressor binding site. This red shift of the phosphorescence along with a corresponding increase in the zero-field splittingE value and narrowing of the ODMR linewidth characterize a binding site that is less polar, as well as more polarizable and homogeneous, than the aqueous solvent. This conclusion is in agreement with the X-ray crystallographic structure of the holorepressor protein that places the indole chromophore of the bound corepressor in a cleft in which it is sandwiched by the side chains of arginines 54 and 84.     

Pressure and volume dependence of thelo-to phonons in InAs

The pressure dependence of thelo-to phonons in InAs has been investigated by Raman scattering using the diamond anvil cell. Indium arsenide transforms, presumably to the rock-salt structure at 70±1 kbar. The mode Grüneisen parameters for thelo-to phonons are γ _lo =0.99±0.03, γ _to =1.2±0.03 respectively. The effective charge,e* _T , for InAs decreases slightly with pressure and this trend is in accordance with the behaviour of other III–V zinc blende structured semiconductors: The structural phase transition is discussed in the light of theoretical calculations for phase stability of III–V compounds, as well as recent high pressure x-ray diffraction studies.     

The Hamiltonian constraint in the teleparallel equivalent of general relativity

In the teleparallel equivalent of general relativity the integral form of the Hamiltonian constraint contains explicitly theadm energy in the case of asymptotically flat space-times. We show that such expression of the constraint leads to a natural and straightforward construction of a Schrödinger equation for time-dependent physical states. The quantized Hamiltonian constraint is thus written as an energy eigenvalue equation. We further analyse the constraint equations in the case of a space-time endowed with a spherically symmetric geometry. We find the general functional form of the time-dependent solutions of the quantized Hamiltonian and vector constraints.     

Classification of Three-Dimensional Integrable Scalar Discrete Equations

We classify all integrable three-dimensional scalar discrete affine linear equations Q ₃ = 0 on an elementary cubic cell of the lattice . An equation Q ₃ = 0 is called integrable if it may be consistently imposed on all three-dimensional elementary faces of the lattice . Under the natural requirement of invariance of the equation under the action of the complete group of symmetries of the cube we prove that the only non-trivial (non-linearizable) integrable equation from this class is the well-known dBKP-system. SPT acknowledges partial financial support from a grant of Siberian Federal University (NM-project No 45.2007) and the RFBR grant 06-01-00814.     

Ga0.47 In0.53 As—The material for high-speed devices

Electron transport properties of Ga_0.47In_0.53As are reviewed. The available physical constants of the material and results on electron mobility in bulk materials, 2deg systems and under hot-electron conditions are presented. Applications of the material in the construction offet’s and photo-conductive detectors are briefly discussed.     

Delayed Fluorescence and Phosphorescence of 8-Aza-d-Homogonane in the Gas and Condensed Phases

The delayed fluorescence spectrum for 8-aza-d-homogonane in the gas phase consists of a band of E-type delayed fluorescence of M-centers and a band of P-type delayed fluorescence of L-centers being the products of photo- and thermotransformations of a basic steroid. Triplet-triplet energy transfer from the M-centers to the L-centers is established and its efficiency is determined. For 8-aza-d-homogonane in frozen hexane solutions at T=77 K only the phosphorescence of the M- and L-centers is revealed. The phosphorescence of the basic steroid itself ( nm) as well as that of the M- and L-centers ( and 532 nm, respectively) is seen in a mixture of frozen tetrahydrofuran and toluene solutions. This is evident of the fact that the basic steroid has the products of its transformations, whose amount grows due to irradiation and heating. The M- and L-centers are stable molecules.     

Electrical second harmonic generation in the autostabilized state of ferroelectric solid solutions (lead,strontium) titanate and (lead,calcium) titanate

tandel effect and second harmonic generation studies on ferroelectric solid solutions (lead, strontium) titanate and (lead, calcium) titanate were carried out near the Curie temperature. The generated second harmonics are linear for low biasing fields with a zero off-set, while they decrease sharply at higher biasing fields. In the autostabilized state, thetandel elements adjust their impedance against the variations of a.c. field. Zero off-set might have been caused due to the presence of delects giving rise to an internal bias which in turn generates second harmonic.     

Recoil corrections to magnetic moments of charmed baryons in themit bag model

Recoil corrections to magnetic moments of charmed baryons are studied in themit bag model. It is noticed that such corrections which improve the octet baryon magnetic moments have considerably significant contributions to charmed baryon’s moments also.     

Approximate angular momentum projection from an intrinsic random phase approximation Hartree-Fock state

An approximation procedure is described to calculate the projected energies from an intrinsicrpa hf wave function. The method of moments is used to find the relevant parameters. A model calculation is carried out for illustrative purposes.