Sharp Spectral Lines Research Articles

Preparation and Fluorescence Spectroscopy of Bulk Monoclinic Eu3+:Y2O3 and Comparison to Eu3+:Y2O3 Nanocrystals

We report the laser spectroscopic characterization of bulk monoclinic Eu3+:Y2O3, which was prepared by a high-temperature, high-pressure synthesis method. The bulk monoclinic phase has sharp spectral lines without the line broadening and “secondary phase” of Eu3+:Y2O3 nanocrystals. The unusual optical properties of site A in this material have been determined to be intrinsic to the monoclinic phase and are not a result of surface effects in the nanocrystals. The 5D0 fluorescence lifetimes are longer in the nanocrystals than in the bulk material, indicating that there is no lifetime shortening in the nanocrystals due to quenching by the proximity of surface defects.

Channeling radiation: Past achievements and future prospects

Abstract When a relativistic charged particle passes through a single crystal very nearly along a major crystalline plane or axis so that it is channeled in that direction, it undergoes periodic motion in the plane transverse to this direction and hence it can radiate. Quantum mechanically, this channeling radiation corresponds to a radiative transition between two eigenstates of the transverse crystalline potential; when the transition occurs between two bound states, a sharp spectral line is emitted. When there are only two bound states (for incident electrons), or when the interplaner potential is nearly harmonic (as for incident positrons), the emitted radiation is nearly monochromatic. Since the discovery of channeling radiation at the LLNL Electron-Positron Linear Accelerator, many of its properties have been delineated, both there and elsewhere. For example, channeling radiation is very intense, forward-directed, easily tunable, and for the planar case, linearly polarized. Channeling radiation has ...

Charge induced H2 spectrum in γ-ray irradiated para-H2 crystals

A sharp spectral line has been observed in γ-ray irradiated para-H2 crystals and assigned to the pure vibrational Q1(0)(v=1←0, J=0←0) transition induced via the Condon effect by charges distributed in the crystal. The remarkable sharpness and stability of the signal is reported and discussed.

Improving Spectroscopic Techniques by a Scanning Multichannel Method

The conventional optical multichannel technique (MT) has improved optical spectroscopy, in comparison to single-channel methods, by at least an order of magnitude in measurement time at the same signal-to-noise ratio. In this work we show that some disadvantages (e.g., limited range of the recorded spectra, different noise and sensitivity of each detection element, and fixed spectral distance of the detection elements) can be excluded by using what we call the scanning multichannel technique (SMT). A calculation of the measurement time for characteristic single-channel and multichannel detectors results in the fact that SMT is, like MT, an order of magnitude faster than the single-channel technique (SCT). In some particular cases SMT results in measurement times shorter than those for MT. We conclude that SMT combines the advantages of MT and SCT. Moreover, measurements of sharp spectral lines made it evident that SMT also improves the reproducibility of the spectrometer used and increases the accuracy of the recorded spectra. The SMT method is not only restricted to optical spectroscopy but can be universally applied to all spectroscopic methods where multichannel detection is used.

Generation of sharp spectral lines under controlled source correlation

Experimentally it has been shown that a single spectral line can be split into many sharp lines under controlled source correlation.

Linewidths of Cu i(511 nm) and Au i(628 nm) laser transitions at room temperature

Sharp spectral lines are obtained for the Cu i 511 nm and the Au i 628 nm transitions from a sputtering-based laser operating at room temperature. The Au i line exhibits a single peak with a linewidth of 360 MHz and the Cu i line consists of three well-resolved peaks with linewidths of 800, 700, and 700 MHz in order of increasing frequency. The spectral lines result from saturated emission on the strongest hyperfine components.

The measurement of integrated intensities

Expressions for the integrated intensities of the Laue and of the rotating-crystal methods are given, which take the spectral distribution of the incident radiation into account. The correlation between the integrated intensities of both methods is elucidated. A procedure is described for the measurement of integrated intensities on an absolute scale using radiation with a continuous spectral distribution superimposed by sharp (spectral) lines. It is shown that crystal-monochromatized radiation may also exhibit, besides sharp lines, continuous tails. Neglecting these tails causes errors up to 2% for observed integrated intensities.

Single-Pulse CARS Apparatus with a Flashlamp-Pumped Dye Laser

Generally, coherent anti-Stokes Raman spectroscopy (CARS) is performed with two dye lasers which are pumped simultaneously by a series of laser pulses from a nitrogen laser or a YAG laser. For biological researches, we need CARS spectra obtained by a single shot of dye lasers. In this case, one of dye lasers is to have a strong and sharp spectral line, and the other has a broad band. Furthermore, it is necessary that two optical beams cross in the sample to satisfy the phase-matching condition. For the samples of liquids and solids, the cross angle is within 1°. This means that two dye laser beams should be thin, parallel, strong enough, and variable independently in each frequency.

The influence of intracollisional interference on the dipole spectrum of HD

The influence of intracollisional interference on the dipole spectrum of pure HD is investigated within the framework of an adiabatic separation of the relative translational motion and non-mixing of rotational levels. The effect leads to a density dependence of the integrated intensities for the sharp spectral lines. It is found that the large discrepancy between the theoretical and experimental pure rotational dipole moment matrix elements for HD reported in the literature can be interpreted as destructive interference between the allowed and the collision-induced dipoles. Similar calculations for the fundamental band are in excellent agreement with the experimental results for the R1(1) line, but agree less well for the R1(0) line. We interpret this, as well as the asymmetrical line shape, as evidence of rotational level mixing due to anisotropic intermolecular forces.

Microwave spectral lines from interstellar dust

SPECTRAL features at 3.07, 10, 20 and 33 µm have proved invaluable in the chemical characterisation of interstellar dust1,2. As spectral observations are extended into the far infrared, it is likely that other features attributable to the absorption and emission of radiation by dust will be observed. To date there has been no discussion in the literature on the possibility of discrete spectral features attributable to dust at even longer wavelengths. The purpose of this note is to suggest that relatively sharp spectral lines may arise from neutral or ionised atomic species in interstellar dust at mm and cm wavelengths. The detection of these spectral features would provide definitive information on the chemical composition of interstellar dust.

Doppler broadening at all temperatures

We discuss the sharp spectral lines emitted by a gas of particles with rest mass m at all temperatures. By treating the problem as fully relativistic we obtain the exact expressions for line shape and total intensity in the two cases where the gas is confined in a box or freely expanding. At all temperatures the Doppler broadening leads to asymmetric shapes with a blue shift of the peak of the line. For relativistic temperatures of the order kT ⋍ mc 2 the line shapes and total intensities are completely different and the free case gives rise to a spectacular increase in total intensity proportional to ( 4kT mc 2 ) 2 . For temperatures of kT > mc 2 4 the line shape changes dramatically and for still higher temperatures the infinitely sharp line emitted in the rest frame of the particles gives rise to a black body spectrum.

Semiconductor lasers pumped by pulsed electric discharge in vacuum

Lasing has been observed in several semiconductors pumped by electrons from a pulsed 5-to 20-kV vacuum arc. This method of pumping eliminates the hot-cathode multielement electron gun and magnetic focusing means usually required for electron-beam generation. At temperatures of 77 K and room temperature, CdS has shown well-defined lasing with narrow directional output and sharp spectral lines. CdSe and GaAs have shown similar evidence of lasing at 77 K. The new technique opens up some possibilities for simple compact laser devices.

Infrared study of solid phosphine

Infrared spectra of two crystalline forms of PH3 and PD3 are reported. The modification studied at 35°K displays broad structureless absorption bands but the form below the transition temperature at about 30°K has a complexity of sharp spectral lines. From results of the temperature effect on the spectra and from studies of isotopic impurities in PH3 and PD3 host crystals, the authors speculate that this lower temperature form of phosphine may have a structure with a primitive cell containing as many as 12 molecules occupying six different sets of sites.

Convergence Zone Propagation in the North American Basin

The long range propagation of a CW 14-Hz signal was studied experimentally. A shallow source was towed across the North American Basin to a maximum range of about 2700 km. The signal was received on a sound channel hydrophone and the envelope recorded. Well-defined convergence zones were observed over the major extent of the tow. The existence of this mode interference wavelength as a sharp spectral line is shown in a power spectrum calculation of the envelope squared versus range.

Coma Canceling Monochromator with No Slit Mismatch

A new plane grating monochromator is described which uses off-axis parabolas. The optical arrangement is such that extremely sharp spectral line images of constant curvature are realized at mirror angles large enough to prohibit the possibility of multiple dispersion.

New Cryogenic Method for Raman Studies of Molecular Crystals

A new technique has been developed for growing good quality molecular crystals, suitable for Raman studies at low temperatures. The method utilizes a copper rod, cooled by a suitable refrigerant, which lies axially in the sample tube. The crystal grows radially around the rod from the melt. Liquid nitrogen and helium cryostats, incorporating this method, for use with the Cary 81 spectrophotometer, are described. These can be readily modified to suit other Raman instruments. Low Rayleigh scattering near the exciting line and the very sharp spectral lines of a number of samples so far studied indicate the good quality of such crystals, grown in a relatively short time.

A TWO-METER NORMAL INCIDENCE VACUUM ULTRA-VIOLET SPECTROGRAPH

摘要 本文叙述了新近建造的一台二米真空紫外光栅摄谱仪的构造、性能和得到的结果,仪器是法线入射式,入射角7.5°,记录波段为2100?—200?。平均色散率为8.7?/mm。应用低气压电容放电光源,获得强而清晰的线状谱,包括大量的高次离化谱线。我们辨认了这个光源发射的大部分谱线共554条。 Abstract A two-meter normal incidence vacuum ultra-violet spectrograph has been built and in operation for some time. The spectrograph has an angle of incidence 7.5° and covers the spectral range 2100?-200?, with an average dispersion 8.7?/mm. A low pressure condensed spark discharge tube is used as the source, giving intense sharp spectral lines of various degree of ionization. Majority (554 in number) of the emission lines has been identified. 作者及机构信息 陶世尧, 王文书, 孙湘 1. 中国科学院物理研究所 Authors and contacts TAO SHI-YAO, WONG WEN-SHU, SUN HSIANG 1. 中国科学院物理研究所 参考文献 [1] 施引文献

Plasma Resonance in the Electrodynamics of Metal Films

When a fast electron passes through a thin metal film it can excite plasma oscillations which then re-radiate the energy in the form of photons. The emitted radiation will appear in a more or less sharp spectral line whose width is the sum of the intrinsic damping rate and the radiative natural line breadth. A completely equivalent formalism is provided by the extension of the theory of transition radiation (semi-infinite metal), to the case of a slab of metal bounded by two parallel planes. In the ideal case of a metal whose dielectric constant contains only a real lossless part, and no imaginary absorptive part, the predicted breadth and strength of the spectral line are the same in both theories. A further phenomenon which is suggested by the plasma-oscillation point of view is the possibility of a resonance in the reflection coefficient of a thin metal film at the plasma frequency, brought about by the collective response of the conduction electrons. The height and breadth of this resonance have been computed and should be observable in relatively ideal cases.

Plasma resonance in the electrodynamics of metal films

When a fast electron passes through a thin metal film it can excite plasma oscillations which then re-radiate the energy in the form of photons. The emitted radiation will appear in a more or less sharp spectral line, whose width is the sum of the intrinsic damping rate and the radiative natural line breadth. A completely equivalent formalism is provided by the extension of the theory of transition radiation (semi-infinite metal), to the case of a slab of metal bounded by two parallel planes. In the ideal case of a metal whose dielectric constant contains only a real lossless part, and no imaginary absorptive part, the predicted breadth and strength of the spectral line are the same in both theories. A further phenomenon which is suggested by the plasma-oscillation point of view is the possibility of a resonance in the reflection coefficient of a thin metal film at the plasma frequency, brought about by the collective response of the conduction electrons. The height and breadth of this resonance has been computed, and should be observable in relatively ideal cases.

Potential Energy Curves for the X 1Σg+ and B 1Σu+ States of Hydrogen

The recently reported accurate data of Herzberg and Howe have been used to calculate the potential energy curves for the X 1Σg+ and B 1Σu+ states of hydrogen by the Rydberg-Klein-Rees (RKR) method. The results are compared with the results of the quantum calculations of Kolos and Roothaan and Dalgarno and Lynn. The agreement is good; in fact, the interaction energy obtained by Dalgarno and Lynn for the ground state agrees with the RKR values to within 2% in the region where the two curves overlap. The rotational predissociation observed in the ν″=14 level of the X 1Σg+ state is discussed. It appears as if there may exist here an unusual case of a sharp spectral line associated with a state which is very close in energy to the maximum of a potential barrier.