Rotation spectra of the polarization plane and circular dichroism of alkaline atoms in strong radiation fields

For alkalineLi, Na, K, Rb, andCs atoms, the Faraday rotation spectra and other effects of the polarization-plane rotation in strong radiation and magnetic fields are investigated. The spectra are calculated by computer simulation of nonlinear resonance magnetooptical polarization effects for real multilevel atoms. The properties of the spectra of different atoms depend on the relationships between the field and spin-orbital interaction energies. Saratov State Technical University. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 5, pp. 25–29, May, 1999.     

Spectrum of the effect of laser radiation on hemoglobin of the blood vessels of skin

We suggested and consider the primary mechanism of biostimulation and of the therapeutic effect of low-level laser radiation caused by a local increase in the effectiveness of oxygen transfer by oxyhemoglobin of the blood vessels of skin. The spectra of the effect of laser radiation on oxyhemoglobin and hemoglobin of the blood vessels of skin are presented which were obtained using a method of numerical simulation with allowance for the optical characteristics of skin and for the depth of penetration into it of radiation of different wavelengths. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 65, No. 6, pp. 877–860, November–December, 1998.     

Spectral measurements of incipient plasma temperature and electron number density during laser ablation of aluminum in air

Plasmas generated during incipient laser ablation of aluminum in air were studied using emission spectroscopy. A plasma emission model was developed, invoking one-dimensional radiative transfer, to describe the observed emission spectra, while taking into account the effects of continuum radiation. Theoretical spectra were calculated and compared to experimental spectra in the range 387–406 nm. Satisfactory agreement was found between the experimental and predicted spectra, especially at delay times of 30–200 ns, thus providing plasma temperatures and electron number densities as functions of delay time and laser irradiance (1.8–8.0 GW/cm²). In general, both the plasma temperature and electron number density rise at greater laser irradiances but drop at increasing delay times, with a more rapid drop for delay times less than 60 ns. PACS 42.62.Fi; 52.25.-b     

Ionization of a molecular hydrogen ion by a strong low-frequency electromagnetic field of laser radiation

Simple analytical expressions are obtained for the energy and angular distributions of outgoing electrons in ionization of a molecular hydrogen ion by a strong low-frequency electromagnetic field as well as for the ionization probabilities per unit time. The cases of linear and circular polarization of the laser radiation are studied. It is shown that in contrast to the case of the ionization of atoms oscillations appear in the energy spectra of the photoelectrons as a function of their kinetic energy. The well-known limits for the tunneling ionization probabilities for the hydrogen atom by a strong low-frequency alternating field are obtained in the case of large internuclear separations. Zh. é ksp. Teor. Fiz. 113, 583–592 (February 1998)     

Intracavity two-photon polarization spectroscopy on the basis of light-induced peaks of radiation power

A calculation of the selective losses of a spectrometer based on a broad-band laser with an anisotropic three-mirror ring resonator containing a two-photon-absorbing atomic gas medium with a light-induced resonance anisotropy has been performed. The conditions under which laser radiation power resonances appear in the output radiation spectrum and the contribution of different factors to their formation have been revealed. Possible ways of obtaining information on the polarization effects induced by a powerful light wave in a medium at the frequencies of two-quantum transitions were investigated. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 66, No. 1, pp. 48–53, January–February, 1999.     

New methods for determining the polarization state of vacuum ultraviolet radiation

Two new methods are proposed for determining the polarization of vacuum ultraviolet radiation which permit the determination of an arbitrary polarization mode for photons with energies of 10–100 eV. The essence of these methods is to create and detect a nonequilibrium population of the magnetic sublevels of atoms and molecules excited by the original VUV radiation and then determine the polarization of this radiation based on these measurements in accordance with known formulas. Zh. Tekh. Fiz. 69, 115–122 (September 1999)     

Influence of laser heating on the optical properties of a superhigh-modulus organoplastic material

The degree and azimuth of polarization and the indicatrix of the intensity of radiation (λ=0.63 μm) reflected by the surface of a monodirectional superhigh-modulus organoplastic material after structural transformations induced in it by CO₂-laser radiation are measured. It is shown that the space-polarization characteristics of the radiation reflected by the organoplastic material charred as a result of laser heating correspond to the parameters of radiation scattered by a nontransparent material with an isotropic surface in the approximation of geometrical optics. B. I. Stepanov Institute of Physics, National Academy of Sciences of Belarus, 68, F. Skorina Ave., Minsk, 220072, Belarus. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 66, No. 5, pp. 635–639, September–October, 1999.     

Spectral polarization characteristics of optical radiation reflected from leaves subjected to unfavorable ecological factors

Angle distributions of the degree and azimuth of polarization of radiation scattered by individual leaves were measured. The polarization characteristics of the reflected radiation were investigated at four radiation wavelengths (460, 550, 680, and 740 nm) and angles of exposure of leaves to light of 60–70°. The experiments were performed with leaves of maples (Acer platonoides) at different stages of vegetation and withering. More than 1000 distributions of the spectral polarization characteristics of the reflected radiation were obtained for maple leaves taken from regions with different ecological conditions during 1993–1995 It was established that the spectral polarization characteristics of the radiation scattered by a leaf markedly change with the state of the leaf. Belarusian State University, 4, F. Skorina Ave., Minsk, 220080, Belarus. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 65, No. 1, pp. 107–113, January–February, 1998.     

Formation of excited states of atoms and ions in laser plasma from CuInS2

Emission spectra and the energy distribution of the excited-state population density of atoms and ions in erosion laser plasma from CuInS₂ with various crystal-structure orderings are analyzed. It is shown that increased ordering of the target crystal structure causes the excited-state energies of indium atoms generated in the laser erosion plume to increase and that sulfur atoms always emit only in transitions from highly excited states. The ratio of relative ion concentrations in the laser plasma plume is Cu⁺/In⁺/S⁺ = 0.3/0.08/2, which corresponds neither to the atomic ratio of Cu/In/S (1/1/2) in the target nor to the ratio of ionization energies. The results are explained by recombination processes for ions and by the atomization specifics of the CuInS₂ target exposed to long-wavelength radiation. The atomization consists essentially of dissociative processes expressed by CuInS₂ → CuInS + S and CuInS₂ → Cu + InS + S. The electron temperature of polycrystal (single-crystal) plasma at a distance of 1 mm from the target is 0.3 eV (0.4 eV) for atoms and 1.3 eV (2.7 eV) for ions and varies negligibly for plasma up to a distance of 7 mm from the target. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 75, No. 2, pp. 217–223, March–April, 2008.     

Spectral and spectral-polarization characteristics of potato leaves

The results of laboratory investigations of the spectral and spectral-polarization characteristics of radiation reflected from the leaves of potato(Solanum tuberosum) of different varieties are discussed. During the vegetation season of 1997, the angular dependence of the degree and azimuth of polarization of radiation reflected from potato leaves as well as the scattering indicatrices in the range 380–1080 nm were determined by a specially developed method with the use of a laboratory goniometric setup. The relationship between the spectral polarization characteristics of radiation and biological parameters of the potato has been obtained with the help of different methods of statistical analysis and explained on the basis of the known physical mechanisms. Translated from Zhurnal Prikladnoi Spektroskopii. Vol. 67, No. 4, pp. 524–529, July–August, 2000.     

Novel technique for transient absorption probing

An original absorption probe technique using a laser plume as a probe source of UV–visible continuum radiation is proposed and tested. To our knowledge, this is the first time that laser plume emission is used as a UV–VIS (190–510 nm) probe beam in transient absorption spectroscopy. The technique allows virtually single-shot recording of continuous fluorescence and absorption spectra and proved its applicability even when used at a high-voltage high-current e-beam gun facility with a high level of electromagnetic interference. The developed technique is applied to record the transient absorption spectra of e-beam-excited Ne, Ar, and Kr gases.     

Probing vacuum birefringence by phase-contrast Fourier imaging under fields of high-intensity lasers

In vacuum high-intensity lasers can cause photon–photon interaction via the process of virtual vacuum polarization which may be measured by the phase velocity shift of photons across intense fields. In the optical frequency domain, the photon–photon interaction is polarization-mediated described by the Euler–Heisenberg effective action. This theory predicts the vacuum birefringence or polarization dependence of the phase velocity shift arising from nonlinear properties in quantum electrodynamics (QED). We suggest a method to measure the vacuum birefringence under intense optical laser fields based on the absolute phase velocity shift by phase-contrast Fourier imaging. The method may serve for observing effects even beyond the QED vacuum polarization.     

Photoinduced optical activity of C<Subscript>70</Subscript> fullerene in organic solvents

We have experimentally studied for the first time the effect of photoinduced rotation of the plane of polarization for pulsed laser radiation in solutions of C₇₀ fullerene in organic solvents and their mixtures. We have shown that the effect is observed for elliptical polarization of the laser radiation and is absent for linear polarization. We present the results of a study of the nonlinear optical characteristics of the C₇₀ solutions. We discuss the physical mechanisms by which nonlinear gyrotropy is induced in solutions. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 76, No. 1, pp. 93–99, January–February, 2009.     

Observation of oriented 23 S 1 helium atoms in a sodium-helium plasma irradiated by polarization-modulated laser radiation

An experiment on the observation of spin polarization of metastable helium atoms interacting with optically oriented sodium atoms under continuous rf discharge conditions is described. Laser radiation with alternating-sign circular polarization, tuned to the resonance excitation of the 3² S _1/2–3² P _1/2 transition in Na atoms, is used as the source for optical pumping of ground-state sodium atoms. Pis’ma Zh. éksp. Teor. Fiz. 65, No. 5, 385–387 (10 March 1997)     

Vibrational spectra of a single crystal of lead germanate and the effect of RS amplification on its surface

For single crystal wafers of lead germanate cut perpendicularly to the C-axis an investigation has been made of IR transmission and RS spectra atλ _exc =632.8, 514.5, and 488 nm in the spectral range of 400–1800 cm⁻¹. An interpretation of the spectra recorded is suggested. In the RS spectra specific features of line intensity distributions are detected. The dependences of the intensity distribution in the peculiarities detected on the excitation wavelength and the angle of incidence of exciting radiation and transmission of the reflected exciting laser beam relative to the optical axis of illumination of the spectrometer inlet slit are investigated. The reason for the occurrence of these specific features is suggested: the interference of RS radiation and exciting laser radiation diffracted on the non-working narrow sides of the diffraction gratings of the spectrometer. The possibilities of amplifying the spectral lines in the RS spectra by imposing diffracted one-mode exciting radiation on them are discussed. Translated from zhurnal Prikladnoi Spektroskopii, Vol. 66, No. 2, pp. 220–226, March–April, 1999.     

Effect of polarization and coherence of low-intensity optical radiation on fish embryos

  We have shown that brief exposure of sturgeon embryos (fertilized roe) in the organogenesis stage to low-intensity radiation in the visible region of the spectrum can have a long-term effect on embryonic and post-embryonic development of the fish, detectable 50 days after the irradiation procedure. The biological effects (size-weight characteristics and hardiness parameters of the fish relative to unfavorable habitat conditions) induced by linearly polarized emission from a monochromatic laser source (helium-neon laser, λ = 632.8 nm, Δλ ≈ 0.02 nm) and a quasi-monochromatic light-emitting diode (LED) source (maximum in emission spectrum λ = 631 nm, Δ λ = 15 nm) are practically the same. Going to broadband linearly polarized radiation (λ = 420–800 nm) is accompanied by a decrease in the biological effect. From the results of studies of the effect on embryos from linearly polarized and unpolarized radiation from an LED source and also the effect of linearly polarized, circularly polarized, and unpolarized radiation from a helium-neon laser, we concluded that the type of polarization is of critical importance in realization of the biological effect of radiation. In this case, the maximum stimulating effect (on the size×weight characteristics and the hardiness parameters for juvenile fish) is observed on exposure to linearly polarized radiation; the photobiological effect induced in the same dose range by light with natural polarization (i.e., unpolarized) is significantly less pronounced; the stimulating effect of circularly polarized radiation occupies an intermediate position. Based on the presented data and also on data obtained previously, we conclude that among the resonant and nonresonant photophysical processes (orientational effect of light, effect of gradient forces, dipole-dipole interactions, thermooptic processes) capable of inducing photobiological effects dependent on such laser-specific characteristics as polarization and coherence, the determining influence in the processes studied in this work comes from the orientational effect of light and dipole×dipole interactions. And the orientational effect can appear for anisotropic media with liquid-crystal type ordering (especially domains in membranes and multiple-enzyme complexes) both under conditions when there is no resonant absorption and for weakly absorbing structures, and can initiate a change in their conformations and accordingly their functional characteristics. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 75, No. 6, pp. 843–858, November–December, 2008.     

Background noise suppression in wide-band lasers with a nonlinear mirror in the cavity

An effective method for suppressing free background generation is proposed. It is based on polarization separation of the narrow-band output radiation of a controlled laser with a nonlinear mirror in the cavity. An increase in the integral ratio between the energy of the narrow generation line and the integral value of the energy of the background over the entire gain band of a wide-band laser from 0.17 to 55.00 has been attained. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 67, No. 2, pp. 169–171, March–April, 2000.     

Radiative corrections for level widths in light muonic atoms

The corrections, which are associated with electron vacuum polarization, for the radiation level widths and line intensities in light muonic atoms are examined. The total level widths, with allowance for the finite size of the nuclei, relativistic effects, and recoil are found. Zh. éksp. Teor. Fiz. 112, 805–817 (September 1997)     

强激光场中H~-离子二维光电子动量谱的理论研究

选用两个模型势,利用强场近似方法研究了H-离子在线性极化强激光场中二维光电子动量谱中次外层后重散射环.研究结果表明:两个模型势中的极化势对二维光电子动量谱的影响很小;随着激光强度的增加,二维光电子动量谱中出现后重散射环的数目变多,沿着次外层后重散射环的光电子的角分布波动性变小,能够通过多项式拟合的方法从二维光电子动量谱中次外层后重散射环获得精确的电子与H原子的弹性散射截面,特别适用于激光强度较小的情况.     

Polarization component method for calculation of the multiple-frequency lasing regime

We have shown that the polarization component method can be extended to the case of broadband emission (multiple-frequency approximation) if we make the approximation of slowly varying amplitudes and statistical independence of the polarization components. From the results of numerical modeling for the case of a liquid dye laser, it follows that the multiple-frequency approximation is meaningful to use for analysis of the spectral, polarization, and energy parameters in the region near and below the lasing threshold, and also for the statistical characteristics but taking into account saturation effects for the laser emission. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 74, No. 3, pp. 346–350, May–June, 2007.