Effect of collisions on the resonance fluorescence spectrum

The effect of collisions on the resonance fluorescence spectrum of two-level atoms excited by monochromatic resonance radiation is studied. Analysis is performed for systems where the Doppler broadening is small compared to the collision frequency (high buffer gas pressures) and for the general case where collisions arbitrarily change the phase of the radiation-induced dipole moment (from completely interrupted to completely unaffected phase of the dipole moment). Both at a relatively low and at a high excitation radiation intensity, the resonance fluorescence spectrum is shown to depend on whether the two-level system is closed or open. This is especially true for the narrow unshifted Rayleigh scattering line. It is shown that, although the absorption line is homogeneously broadened, the resonance fluorescence spectrum exhibits a clearly pronounced anisotropy. In a direction close to the direction of propagation of the excitation radiation, the Rayleigh scattering line is maximally narrowed. Under certain conditions (that can easily be created in experiments), the width of this line is proportional to the diffusion coefficient of atoms interacting with the radiation.     

Time modulation of recoilless nuclear resonance fluorescence

The time dependence of the resonance fluorescence of nuclei excited by the spontaneous radiation of identical nuclei is studied. Particular attention is paid to the influence of the periodic overlap of the source on the form of the scattered radiation line and it is shown that the line may even split. A mechanical filter permitting measurement of pure radiation scattering is calculated.     

Excitation transfer from second to first resonance line of potassium observed in hot atomic vapor

We present experimental investigation on the fluorescence profiles observed by excitation of the hyperfine transitions of the second resonance line of potassium with a wavelength of 404.4 nm in dependence on the atomic density. This leads to both direct decay of the excited level population to the ground state (violet fluorescence), and to cascade decay via the first resonance lines (infrared fluorescence). It has been shown that the behavior of these two fluorescence profiles is different: increasing the atomic density, the violet fluorescence profile exhibits a well-pronounced self-absorption dip, while the infrared line does not show any narrow-width reduced absorption structure. Moreover, the profiles of the infrared line have a higher signal-to-noise ratio than that of the violet line. Our investigations show that beside atomic population, atomic polarization is also transferred by the cascade transitions. This is evidenced by registration of coherent magneto-optical resonances at the two fluorescence lines. The signal-to-noise ratio of these resonances registered at the first resonance line is significantly higher than at those obtained at the second resonance line. The proposed study makes it possible to examine cascade transitions in alkali atoms, particularly the preservation of atomic polarization, i.e. the coherence transfer by cascade transitions.     

Quantum memory on a charge qubit in an optical microresonator

Polarized fluorescence decay in NADH molecules in aqueous solution under two-photon excitation by femtosecond laser pulses has been studied. The excitation was carried out by linear and circularly polarized radiation at four wavelengths: 720, 730, 740, and 750 nm. Time-dependent polarized fluorescence signals were recorded as a function of the excitation light polarization and used for determination of a set of molecular parameters, two lifetimes characterizing the molecular excited states, and the rotation correlation time τ_rot. The results obtained can be used to create and prove theoretical models describing the intensity and polarization of fluorescence in NADH involved in the regulation of the redox reactions in cells and tissues of living organisms.     

The excitation and emission of terahertz surface plasmon polaritons on metal wire waveguides

The development of effective techniques for guiding pulsed terahertz radiation is essential for the continued development of terahertz spectroscopy and imaging applications based on the technique of time-domain spectroscopy. Terahertz surface plasmon polaritons (SPPs) can be excited and guided on cylindrical metal wires with low loss and dispersion. This propagating surface wave, known as a Sommerfeld wave, possesses radial polarization, which is not well matched with conventional sources of pulsed terahertz radiation. A photoconductive terahertz antenna with radial symmetry produces radiation that more efficiently couples to the wire waveguide. At the end of the wire, terahertz SPPs emit radiation into free-space that exhibits frequency-dependent diffraction. To cite this article: J.A. Deibel et al., C. R. Physique 9 (2008).     

Radiation of electrons in a synchrotron with rectilinear gaps

The spectral, angular, and polarization properties of the synchrotron radiation of electrons moving in a synchrotron or storage ring are investigated in this paper with allowance for the rectilinear gaps of these facilities. It is shown that a frequency-dependent asymmetry with respect to the azimuthal angle of observation must be observed in this case in the spectral and angular distribution of the radiation energy.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 12, pp. 67–72, December, 1986.     

用偏振荧光光谱表征乙醇-水团簇分子的取向行为

采用波长为236nm紫外光激励乙醇水溶液获得荧光光谱并对其偏振特性进行了研究.实验中分别改变入射光的偏振度，在300—400nm波段内进行荧光光谱、水平和垂直偏振荧光光谱检测.实验结果表明，当采用线偏振光照射乙醇水溶液时，其发射的荧光具有一定的偏振性，并计算了其偏振度.经理论分析得到了描述荧光偏振态的四个斯托克斯矢量，进而对该荧光的偏振状态进行了描述，通过对乙醇-水溶液的米勒矩阵的计算，对溶液中分子的取向特性进行了分析.本结果能对乙醇-水团簇分子的结构提供理论参考. 关键词： 荧光光谱 偏振光谱 斯托克斯矢量 米勒矩阵     

Single nanoparticle quantum dynamics studied by the photon distribution function

The blinking fluorescence of a single nanoparticle excited by CW laser radiation was studied. In the case of a low time resolution setup, blinking fluorescence appears to be a continuous emission. Blinking can nevertheless be established if we measure the photon distribution function in such quasi-continuous fluorescence.     

Mathematical modeling of random coupling between polarization modes in single-mode optical fibers: XVI. Depolarization and repolarization of polychromatic radiation in single-mode optical fibers with random inhomogeneities

The dependences of the degree of polarization of polychromatic radiation on the length of a single-mode optical fiber (SMF) with random inhomogeneities have been obtained by mathematical modeling. The case is considered where radiation having both polarization modes excited with equal weights of linear polarization is first introduced into a depolarizer of polychromatic radiation (a SMF segment with high linear birefringence) and arrives at an SMF with low linear birefringence. It is shown that the degree of polarization of radiation after transmission through the first segment becomes significantly suppressed and remains almost constant upon propagation through the second segment, after which it begins to sharply increase at some length; i.e., repolarization of radiation occurs. It is shown that repolarization of radiation depends weakly on the angle made by the axes of unperturbed linear birefringence of the first and second segments. The conditions for the length of the first segment (depolarizer) under which the degree of polarization remains minimum throughout the second segment are determined.     

LiYF4:Nd3+的发光

首次研究了LiYF4:Nd3+由Ar+激光5145Å激发的发光(Laser excited photo-luminescence,LEPL)以及由X射线激发的发光(X-Ray excited photo luminescence,XEPL).仔细地研究了它的荧光谱的偏振特性.     

血清浓度变化对血清荧光光谱的影响

光谱分析技术应用于血液的某些疾病诊断具有方便、快速的特点.文章采用日本岛津荧光光度计RF5301,研究了血清荧光光谱随血清浓度变化的规律,为通过血液分析进行疾病诊断提供了实验依据.实验结果表明:在不同波长的激发光激励下产生的荧光光谱不同,当用220,230,310～420 nm波长的光激发时,血清的荧光强度随着血清浓度的增加越来越大;而采用240～300 nm波长的光激发时,血清的荧光强度随着血清浓度的增加变得越来越小.实验还发现:当采用220,230,310～420 nrn波长的光激发时,血清的浓度猝灭和吸收作用不明显,主要是激发出的荧光起作用;采用240～300 nm波长的光激发时,血清浓度猝灭和吸收作用明显,导致荧光强度随着血清浓度的增加变得越来越弱.这对研究血清荧光光谱时血清浓度的选择具有参考价值.     

Experimental dependence of two-photon absorption efficiency on statistical properties of laser light

The fluorescence intensity excited by two-photon absorption of the 514.5 nm argon laser line has been investigated for various oxasol derivatives. The fluorescence intensity was dependent on the statistical properties of the 514.5 nm argon laser line and was a factor 1.52-1.86 larger for absorption of a multifrequency laser line than in the case of a single frequency laser line.     

The influence of quantum interference effects on the resonance fluorescence spectra of a degenerate three-level atom

The resonance fluorescence spectra of a degenerate three-level atom of the V-type in the field of an intense monochromatic wave with an arbitrary polarization composition are investigated. Analytical expressions are derived for the resonance fluorescence spectra, and the angular distribution of spontaneous fluorescence of atoms is analyzed for the D-line emitted by vapors of alkali atoms. It is shown that the number of lines in the spectrum may decrease in the case of the linear polarization of spontaneous radiation. The radiation relaxation operator is obtained for the D-line of alkali metals in the case when an atom is near the metal surface. Interference effects for such systems are analyzed.     

Effect of magnetic field on the character of fluorescence of dense and cold atomic ensembles excited by pulsed radiation

Specific features of fluorescence of dense and cold nondegenerate atomic ensembles in an external constant magnetic field are analyzed theoretically. The angular distribution, polarization properties, as well as the spectral composition of fluorescence radiation are calculated. The time variation of these characteristics after the end of the excitation pulse is analyzed. The dependence of the properties of secondary radiation on the duration and carrier frequency of the pulse is investigated. It is shown that, for dense clouds in which the free path length of quasiresonance photons is commensurate with the interatomic distance, the magnetic field significantly modifies all the observable properties of the radiation. Under these conditions, the trapping time may increase by tens of times. Magnetic field enhances the effect of quantum beats observed on time scales commensurate with the lifetime of the excited states of atoms. For individual polarization channels, this field also intensifies the phenomenon of coherent backscattering (CBS). The phenomena found are explained by the effect of magnetic field on the character of resonance dipole–dipole interaction and, as a result, on the specific features of collective phenomena in dense atomic ensembles.     

Polarization of the Fluorescence Excited in the P- and R Branches of the Vibronic Lines of Jet-Cooled Complex Molecules

A model is suggested to calculate the degree of polarization of the fluorescence of jet-cooled polyatomic molecules excited within the P- and R branches of the rotational contour of the vibronic line by light not providing resolution of the rotational structure. These dependences are calculated and compared with experimental data for molecules belonging to different types of asymmetric tops with different intramolecular orientation of the fluorescence transition dipole moment: anthracene; anthracene + Ar; 1,4-diaminoanthraquinone; indole; tetracene, and triphendioxazine.     

Polarisationseffekte des Fluoreszenzlichtes von Anthrazenkristallen und Plastikszintillator in Abhängigkeit von Deuteronenenergie und Temperatur

Investigations of the optical isotropic plastic scintillator showed that the fluorescence light is more polarized perpendicular than parallel to the particle impact direction. Furtheron the fluorescence light polarization of anthracene crystals proved to be dependent on particle impact direction. Both the degree of fluorescence light polarization of plastic scintillator and the dependence of fluorescence light polarization of anthracene crystals could be explained by the mechanism of energy travelling from direct excited to light emitting molecules.     

Polarization studies of radiation emitted by surface plasmons in silver

Measurements are reported on the polarization of radiation emitted by the roughness induced decay of nonradiative surface plasmons optically excited by light in thin Ag films. This radiation is of mixed polarization when the incident light is p-polarized. The s-polarized component of the radiation is observed to be considerably less intense than the p-polarized component.     

异丙醇-水配合液的荧光偏振和时间分辨特性

研究了紫外光照射下异丙醇-水配合液的偏振荧光光谱,以及不同荧光峰处光子强度随时间的衰变过程,计算了偏振度并讨论了其偏振特性,测试了不同峰位对应的荧光寿命并分析了其荧光发射特性.结果表明,异丙醇-水配合液在紫外光激励下发射的荧光为具有确定分子取向的部分偏振光,偏振度和各向异性度分别为0.542和0.441.在波长为220...     

Implementation of a double-scanning technique for studies of the Hanle effect in rubidium vapor

We have studied the resonance fluorescence of a room-temperature rubidium vapor exited to the atomic ⁵P_3/2 state (D₂ line) by powerful single-frequency cw laser radiation (1.25 W/cm²) in the presence of a magnetic field. In these studies, the slow, linear scanning of the laser frequency across the hyperfine transitions of the D₂ line is combined with a fast linear scanning of the applied magnetic field, which allows us to record frequency-dependent Hanle resonances from all the groups of hyperfine transitions including V- and Λ-type systems. Rate equations were used to simulate fluorescence signals for ⁸⁵Rb due to circularly polarized exciting laser radiation with different mean frequency values and laser intensity values. The simulation show a dependence of the fluorescence on the magnetic field. The Doppler effect was taken into account by averaging the calculated signals over different velocity groups. Theoretical calculations give a width of the signal peak in good agreement with experiment.     

Level mixing induced transparency for gamma radiation

The propagation of gamma radiation through a resonant medium in the case of interfering quantum transition paths is considered. The interference is made possible by a field that mixes the crossing spin levels in the excited nuclear state and splits two degenerate transitions into two V-type transitions. If forward resonant scattering allows for a change of the gamma radiation polarization, then the two V-transitions are coupled, which results in destructive interference. In this case the absorption is reduced in a particular frequency domain. PACS 42.50.Gy; 33.45.+x