Light Curve Models of Supernovae and X-ray spectra of Supernova Remnants

We compare parameters of well-observed type II SN1999em derived by M.Hamuy and D.Nadyozhin based on Litvinova-Nadyozhin (1985) analytic fits with those found from the simulations with our radiative hydro code Stella. The difference of SN parameters is quite large for the long distance scale. The same code applied to models of SN1993J allows us to estimate systematic errors of extracting foreground extinction toward SN1993J suggested by Clocchiatti et al. (1995). A new implicit two-temperature hydro code code Supremna is introduced which self-consistently takes into account the kinetics of ionization, electron thermal conduction, and radiative losses for predicting X-ray spectra of young supernova remnants such as Tycho and Kepler.Comment: 7 pages, 10 figures, Supernovae as Cosmological Lighthouses, Padua, June 16- 19, 2004, eds. M.Turatto et al., ASP Conference Serie

Helium 2 3S - 2 1S metrology at 1557 nm

An experiment is proposed to excite the 'forbidden' 1s2s 3S1 - 1s2s 1S0 magnetic dipole (M1) transition at 1557 nm in a collimated and slow atomic beam of metastable helium atoms. It is demonstrated that an excitation rate of 5000 /s can be realised with the beam of a 2W narrowband telecom fiber laser intersecting the atomic beam perpendicularly. A Doppler-limited sub-MHz spectroscopic linewidth is anticipated. Doppler-free excitation of 2% of trapped and cooled atoms may be realised in a one-dimensional optical lattice geometry, using the 2W laser both for trapping and spectroscopy. The very small (8 Hz) natural linewidth of this transition presents an opportunity for accurate tests of atomic structure calculations of the helium atom. A measurement of the 3He - 4He isotope shift allows for accurate determination of the difference in nuclear charge radius of both isotopes.Comment: accepted for publication in Europhysics Letter

Estimation of Crystal Sample Structure by Means of Fast Electron Radiation

An analysis is made of the dependence of the characteristics of X-ray radiation arising during the passage of fast electrons through the crystal on the quality of the internal structure of the sampleyesBS

Narrowband Biphoton Generation due to Long-Lived Coherent Population Oscillations

We study the generation of paired photons due to the effect of four-wave mixing in an ensemble of pumped two-level systems that decay via an intermediate metastable state. The slow population relaxation of the metastable state to the ground state is utilized to create long-lived coherent population oscillation, leading to narrowband nonlinear response of the medium. The biphotons have a narrow bandwidth, long coherence time and length, which can be controlled by the pump field. In addition, the biphotons are antibunched, with antibunching period determined by the dephasing time. During this period, damped oscillations of the biphoton wavefunction occurs if the pump detuning is non-zero.Comment: 7 pages, 2 figure

Influence of crystal mosaicity on the X-radiation characteristics observed at a small angle to the particle velocity direction

The experimentally measured yields of X-rays generated by 500-MeV electrons in oriented tungsten single crystals are analyzedye

Calculation of the X-ray reflectivity of b-class mosaic crystals via the Monte Carlo method

b-class mosaic crystals, including pyrolytic graphite, are widely used as neutron and X-ray monochromators in experimental physics and ensure a more intense yield of monochromatic radiation than do perfect crystalsye

Calculation of class-b mosaic crystals reflactivity by Monte Carlo techniqye

The technique is proposed and implemented to calculate the reflectivity of such crystals by Monte Carlo modeling, corrently considering the multiple reflections of photons inside the crystal and the geometry of experiment for random distribution of the mosaicyesBelgorod State Universit

Influence of crystals mosaicity on observed characteristics of X-ray emission along the propagation velocity of fast electrons in thick tungsten crystals

The results of a set of experiments on X-ray emission yield of ω ∼ γωp energy, generated by 500MeV energy electrons in oriented tungsten single crystals are presented. The experiments were performed at Tomsk synchrotron using Crystal grating spectrometers based on mosaic crystals of pyrolytic graphite. It is shown that the measurement results are caused by the competition of two mechanisms: parametric X-ray emission along the particle velocity and bremsstrahlung diffraction in mosaic crystals of aα group. A method for determining the characteristic bulk dimensions in mosaic crystals of aα group is suggested