Primary extinction in resonantγ-ray scattering

A general expression is derived for the primary-extinction length, which in resonant scattering is less by two orders of magnitude than for nonresonant scattering, though there are directions in the crystal for which it increases considerably.I am indebted to D. F. Zaretskii for discussions.     

On the spectra of resonant coherent Raman scattering

The spectra of resonant coherent anti-Stokes and Stokes Raman scattering of excited molecules are calculated and discussed. The interaction of light and molecules is treated semi-classically. The energy level diagram of four energy levels describing the process is used in four modifications possible for excited molecules. It is shown that non-vibrational resonances give extra maxima in some of the spectra. Comparison of the spectral structure in the Stokes and anti-Stokes components gives information on which of the four schemes the interaction is realized by. The influence of the pumping detuning on the Stokes component shape is pointed out.     

Calculation of nuclear resonant scattering spectra of magnetic multilayers

We report on calculations of the angle- and time-dependent photon reflectivity of multilayers using the technique of characteristic matrices. Spectra of⁵⁶Fe/⁵⁷Fe and Cr/Fe multilayers are calculated under various conditions. The parameters of the multilayers are optimized for suitable test samples of reflectometry measurements.     

Isotope effect in resonant Raman scattering and induced IR spectra of trans-polyacetylene

We present a full explanation of the isotope effect in resonant Raman scattering, doping induced, and photo-induced IR-active vibrations of previously reported data in trans-(CH)_x, (¹³CH)_x and (CD)_x. The interpretation is given in terms of Raman scattering from amplitude modes of the dimerized chains and absorption by charged induced IR-active modes. It is shown that the bare phonon frequencies are properly modified by the isotope mass whereas the observed frequencies are derived by the dressed phonon propagator, and therefore do not follow the usual mass rule.     

Quantum-mechanical analysis of the intensity distribution in spectra of resonant Raman scattering spectra of aqueous solutions of tyrosine

Quantum-mechanical calculations of the intensity distribution in the resonant Raman scattering spectra of aqueous solutions of tyrosine excited by laser radiation with wavelengths of 244, 229, 218, 200, and 193 nm, as well as in the nonresonant Raman scattering spectrum excited at a wavelength of 488 nm, are performed. Satisfactory agreement is achieved between the calculation results and the experimental data. It is shown that the changes in the intensity distribution observed in the spectra with a change in the excitation wavelength from 244 to 193 nm correlate with the determined changes in the contribution made by excited electronic states into the scattering tensor components. It is noted that it is necessary to take into account the Herzberg–Teller effect and that the number of excited electronic states taken into account considerably affects the calculated relative intensities of lines. The possibility of existence of several tyrosine conformers in aqueous solution at room temperature is shown.     

On the spectra of gamma-ray bursts

Summary One of the possible interpretations of the spectra of gammaray bursts is in terms of synchrotron emissivity of mildly relativistic electrons. In this case, the shape of the spectra depends on the angle between the magnetic field and the observer. We show here that, although this angle can be important for single events, the statistical properties of gamma-ray bursts are determined essentially by those events for which this angle is near π/2, namely events observed in the direction of maximum emitted flux. Paper presented at the 2° Convegno Nazionale di Fisica Cosmica, held at L'Aquila, 29 May–2 June 1984.     

Unveiling the secrets of gamma ray bursts

Gamma Ray Bursts are unpredictable and brief flashes of gamma rays that occur about once a day in random locations in the sky. Since gamma rays do not penetrate the Earth's atmosphere, they are detected by satellites, which automatically trigger ground-based telescopes for follow-up observations at longer wavelengths. In this introduction to Gamma Ray Bursts we review how building a multi-wavelength picture of these events has revealed that they are the most energetic explosions since the Big Bang and are connected with stellar deaths in other galaxies. However, in spite of exceptional observational and theoretical progress in the last 15 years, recent observations raise many questions which challenge our understanding of these elusive phenomena. Gamma Ray Bursts therefore remain one of the hottest topics in modern astrophysics.     

Temperature dependence of phonon energy spectra with nuclear resonant scattering of synchrotron radiation

Summary The phonon energy spectra of a polycrystalline α-Fe foil were observed at 150 K and 300 K by using the nuclear resonant scattering of synchrotron radiation. In each spectrum, inelastic scattering was observed at both sides of the elastic peak. It was found that the ratio of the elastic-scattering component and the asymmetry of the intensity of the side bands observed at 150 K are larger than those observed at 300 K, respectively. The observed temperature-dependent spectra are in good agreement with the spectra calculated from the phonon energy distribution function. One of the advantageous features of this method is that the excitation of only a specific element is possible. Our results show that this method is applicable to the study of lattice dynamics and opens a new field of the nuclear resonant scattering spectroscopy. Paper presented at ICAME-95, Rimini, 10–16 September 1995.     

用γ射线做康普顿散射测量

用能量为661.67keV的γ射线做不同材料散射靶的康普顿散射,对是否有多个电子同时与同一γ射线散射进行了分析.测量了电子质量,分析了相干散射线宽,测量了非相干散射光子的能量,算出了非相干散射微分截面,给出了Θ~Θ dΘ内散射光子微分截面与散射角关系.     

Non-statistical effects in neutron capture γ-ray spectra

A search for non-statistical effects in γ-ray spectra following neutron capture has been made for incident neutron energies in the range 40 keV to 1 MeV. The experiments were performed using a 20 cm × 15 cm Nal detector; thirty elements ranging from calcium to uranium were examined. Marked non-statistical effects were found in the spectra from elements in the mass regions where the 3s, 3p and 4s neutron strength functions maximize. Results from the first two regions could often be explained in terms of enhanced transition strengths to final states with a strong single-particle nature.