首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 78 毫秒
1.
Tunable single-line first-overtone (FO) CO lasing on wavelengths from 2.7 up to 4.2 μm corresponding to overtone vibrational transitions from 13→11 up to 38→36 on 413 ro-vibrational lines was experimentally obtained. A parametric study of energetic and spectral characteristics of the single-line FO CO laser was carried out. Energy distribution over ro-vibrational lines was measured. The maximum specific output energy (SOE) came up to 3 J/l Amagat, with single-line output efficiency being up to 0.6%. For the first time, a multi-quantum theoretical model was used to describe the tunable single-line FO CO laser. This multi-quantum approach demonstrated better agreement between theoretical calculations and observed experimental data for laser output as a function of vibrational quantum numbers.  相似文献   

2.
The equilibrium statistical volume distribution in foams, which has been previously demonstrated to be the so-called log-normal, is accounted on probability grounds by a scaling law on the bubble's volume time-evolution. This law states that the conditional probability for a given bubble to have the volume v(t + Δt), he assumption that it was v(t), to depend solely on the relationship v(t + Δt)/v(t), and in particular, to be independent of the time t. The theoretical results, however, allow to go further. Indeed, since the time dependece of its parameters (expectation and variance) are given functions of time, only two parameters are necessary to describe completely the foam.  相似文献   

3.
In the present work it is demonstrated that a wideband CO laser operating at fundamental and overtone vibrational transitions is a promising source of laser radiation for remote laser sensing of the atmosphere. A compact slab RF-discharge CO laser has been designed. The optimal operating conditions are determined for this CO laser. In experiments, the maximum average output laser power was ∼12 W for lasing efficiency of ∼14%. Under fixed experimental conditions, stable lasing (with fluctuations of the output laser characteristics ≤5%) was observed during more than one hour, which suggests that we first excited the sealed-off mode of cryogenic slab RF-discharge CO laser. The frequency-selective mode was first obtained for this laser. Wavelengths for sensing of nitrous oxide, nitrogen dioxide, methane, formaldehyde, and some other gases on near-ground propagation paths are determined. Our experiments and calculations confirm that this CO laser is promising for laser gas analysis. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 11, pp. 76–83, November, 2008.  相似文献   

4.
Spectral characteristics of a two-section laser structure with δ-doping active regions are studied theoretically. The wide range of tuning of the lasing wavelength is primarily related to specific characteristics of the gain spectra of n-i-p-i crystals: the dependence of the effective band-gap width of the superlattice on the level of excitation, the character of variation of the overlap integrals of the electron and hole wave functions, and broadening of the electronic spectra due to fluctuations of the electrostatic potential. Depending on the pumping currents in sections of the laser structure, the lasing wavelength can be tuned over a wide spectral range of the IR region in regimes of cw lasing, the transient regime, and the regime of regular pulsations. In the regime of self-sustaining pulsations, lasing is also possible at two wavelengths spaced well apart.  相似文献   

5.
Spectral transmittance measurements have been performed in the v6-fundamental of 12CH3D at 153 K. Relevant to the studies of the emission spectra of Titan recorded by the IRIS instruments on board Voyagers 1 and 2, N2 has been used as the broadening gas. Excellent agreement between experimental and theoretical spectral transmittance has been the result of using N2-broadened line widths and their dependence upon temperature measured by us in the v2-fundamental and S = 63.6 cm-2 atm-1 for the absolute intensity of the v6-fundamental.  相似文献   

6.
The reaction γp → π°γ′p has been measured with the TAPS BaF2 calorimeter at the Mainz Microtron accelerator facility MAMI for energies between √2 = 1221–1331 MeV. Cross sections differential in angle and energy have been determined for the photon γ′ in three bins of the excitation energy. This reaction channel provides access to the magnetic dipole moment of the Δ+(1232) resonance and, for the first time, a value of μΔ+ = (2.7+1.0−1.3(stat) ± 1.5(syst) ± (theor)) πN has been extracted.  相似文献   

7.
The experimental and theoretical study of lasers working on the first vibrational overtone of the CO molecule is reviewed. A theoretical model of the active medium of the CO laser and its verification are presented. The CO laser operation in a wide spectral range (2.5–4.2 μm) that spans the atmospheric transparency window is demonstrated in the review of experimental works. It is shown that the overtone CO laser can serve as an effective mid-IR source for atmospheric spectroscopy, long-distance transportation of laser radiation, remote laser sensing, etc.  相似文献   

8.
We report an experimental investigation on the Doppler-free saturated absorption spectroscopy of buffer-gas-cooled Barium monofluoride (BaF) molecules in a 4 K cryogenic cell. The obtained spectra with a resolution of 19 MHz, much smaller than previously observed in absorption spectroscopy, clearly resolve the hyperfine transitions. Moreover, we use these high-resolution spectra to fit the hyperfine splittings of excited A(v = 0) state and find the hyperfine splitting of the laser-cooling-relevant A2Π1/2(v = 0, J = 1/2,+) state is about 18 MHz, much higher than the previous theoretically predicted value. This provides important missing information for laser cooling of BaF molecules.  相似文献   

9.
We studied the coercivity in magnets of composition R17Fe83−χBχ (R = Nd, Pr and χ = 8, 30), using measurements of the coercive field Hc, its angular dependence, and the magnetic viscosity coefficient Sv, for temperatures between 4.2 and 500 K. The results are discussed in relation to a model which does not specifically consider the detailed mechanisms involved in magnetization reversal, but which provides information about the magnetic properties in the activation volume v where magnetization reversal is initiated. It is concluded that the ordering temperature in v tends to be slightly smaller than in the bulk and that the room temperature anisotropy in v is not strongly reduced with respect to the bulk value. Finally, a direct evaluation of the dipolar interactions is in good agreement with results obtained from Hc(T).  相似文献   

10.
Band structures of 76Se and 78Se have been studied with the 74,76Ge(, 2nγ)76,78Se reactions by using a variety of in-beam γ-techniques : γ-ray singles spectra, γ-ray excitation functions, γ-γ-t coincidences, γ-ray angular distributions and γ-ray linear polarizations.

Spins and parities have been assigned uniquely for many new levels in 76Se and 78Se and four bands have been identified in both nuclei: (i) the ground-state band, (ii) a positive-parity ΔJ = 1 band built on the second 2+ state (γ-vibrational band), (iii) a negative-parity Δ J = 2 band built on the 3 state (octupole band) and (iv) a ΔJ = 2 band built on the high-lying J = 4 state. In addition, the second 8 + and 10+ states, which are possibly the lowest members of a band, have been found in both nuclei.

Systematics of the band structures obtained are discussed. Level energies of the band members and B(E2) ratios for some of the inter-band transitions between γ- and ground-state bands have been calculated with the proton-neutron interacting boson model IBM-2 and a reasonable agreement with the present data has been obtained.  相似文献   


11.
The nonlinear dynamics of a loss-modulated, two-wave CO2 laser lasing on vibrational–rotational lines of different vibrational bands has been investigated theoretically and experimentally. It is shown that the time and energy parameters of laser radiation can be controlled within fairly wide limits by changing the depth and frequency of modulation and the ratio between the constant components of the losses.  相似文献   

12.
E. Danicki 《Ultrasonics》1993,31(6):421-424
A theory of a reversing multistrip coupler (RMSC) is presented based on a previously developed spectral theory of IDTs. It shows that the frequency dependence of the track-changing reflection of a SAW taking place in a RMSC, and the dependence of the reflection of the SAW from a periodic grating reflector are described by the same functions. The reflection of the SAW to the other channel is complete in a narrow frequency band of relative width (2/3) Δv/v if the RMSC is sufficiently long. Several expected applications of RMSCs are discussed, among them SAW dispersive filters, resonators, and low-loss filters.  相似文献   

13.
We introduce a new parameterization of four-fermion operator matrix elements which does not involve quark masses and thus allows a reduction of systematic uncertainties. In order to simplify the matching between lattice and continuum renormalization schemes, we express our results in terms of renormalization group invariant B-parameters which are renormalization-scheme and scale independent. As an application of our proposal, matrix elements of ΔI=3/2 and SUSY ΔS=2 operators have been computed. The calculations have been performed using the tree-level improved Clover lattice action at two different values of the strong coupling constant (β=6/g2=6.0 and 6.2), in the quenched approximation. Renormalization constants and mixing coefficients of lattice operators have been obtained non-perturbatively. Using lowest order χPT, we also obtain ππ|O7|KNDRI=2=(0.11±0.02) GeV4 and ππ|O8|KNDRI=2=(0.51±0.05) GeV4 at μ=2 GeV.  相似文献   

14.
Excitation spectra for dispersed VUV-fluorescence of NO (λfl=134–152 nm) were measured in the exciting-photon energy range between 16.9 and 24.8 eV using monochromatised synchrotron radiation at medium bandwidth of 29 meV. Fluorescence from A1Π (vi=0, 1, 2) vibronic NO+-levels and fluorescence from excited dissociation fragments NI (3s 2PJ) was observed simultaneously by recording the dispersed fluorescence with a monochromator–position-sensitive detector combination. The autoionisation of NO (c3Π) nℓλ (vR=0) Rydberg levels into the NO+ A1Π (vi=0, 1, 2) vibronic levels was observed vibrationally resolved. Different Beutler–Fano profiles for autoionisation of one Rydberg level NO (c3Π) nℓλ (vR=0) into the different vibronic NO+ A1Π (vi=0, 1, 2) levels are clearly visible. The dependence of the Beutler–Fano profiles on the quantum numbers n, , and λ of the Rydberg electron is discussed. For the direct photoionisation into the NO+ A1Π (vi=0, 1, 2) vibronic levels a non-Franck–Condon behaviour was observed.  相似文献   

15.
Using quasi-static fields and pulsed fields we have measured the magnetization rate dM/dt = v as a function of field H for Dy3Al2 and DyCoNi which present narrow domain walls. The experimental results follow the empirical law v = v∞ exp (−Ho/H). An analogous experimental law has been observed for domain reversal in ferroelectrics and for dislocation motion.  相似文献   

16.
We report the development of a new series of laser dyes and describe the performance of these materials. This work was spurred by the realization that few laser dyes have an optimally shaped fluorescence emission for lasing action. Most of the dipole strength of the transition is concentrated in the 0.0 band, where lasing cannot occur, and very little is concentrated in the vibrational satellites 0–1 and 0–2 where lasing is possible. The new dyes are unsymmetrical materials which may be considered as a hybrid of a rhodamine molecule and a fluorescein molecule (fig. 1), and we consider them to be cyclized merocyanines. One dye in particular, 6-dimethylamino-9-o-carboxyphenylxanthen-3H-one (labelled SNH-8), has given power output and time stability better than the preferred lasing dye Rhodamine 6G. The effects of dye structure and of acid-base transitions on lasing activity will be discussed briefly. The theory of band-shaping and the detailed optical parameters of the new dyes will be presented separately.  相似文献   

17.
An electric-discharge carbon monoxide broadband overtone laser has been developed. The laser is capable of lasing on CO first overtone bands only (Δv = 2) and delivering up to 12 W cw power at efficiencies of up to 5%. The laser output consists of vibrational-rotational lines of the v = 9 → 7 to v = 35 → 33 overtone bands and covers the spectral range between 2.6 and 3.9 μm. Totally about 40-45 lines could be observed in the laser spectrum simultaneously. A kinetic modeling code has been developed to predict the power, efficiency, and the output spectrum of the CO overtone laser.  相似文献   

18.
A. R. Burns 《Surface science》1993,280(3):349-358
The first quantum-resolved angular distribution measurements of electronically-excited neutral molecules which have undergone electron stimulated desorption (ESD) are presented. Two-dimensional imaging of laser resonance-enhanced multiphoton ionization (REMPI) is used to obtain angular distributions of CO* in the v=0 vibrational level of the metastable a3Πr state desorbed from CO/Pt(111) by 350 eV electrons. For saturation CO coverages at 90 K, sharp Gaussian distributions peaked about the surface normal (6° ± 0.5° half-width at half maximum) are observed, consistent with previously reported data acquired by ESDIAD (ESD ion angular distributions). The (1 + 1) photon REMPI scheme for state-specific CO* detection involves the b3Σ(v = 0) ← a3Π(v = 0) transition at 283 nm, followed by photoionization at the same wavelength. In this paper, the overall experimental technique for REMPI imaging of products from electron stimulated processes is discussed. Thus specific CO* data as a function of coverage and temperature is presented for comparison with the ESDIAD results.  相似文献   

19.
Formally dipole-forbidden adsorbate vibrational modes have recently been detected using infrared reflection-absorption spectroscopy (IRAS). In an earlier publication we have proposed that the excitation of these modes is indirect, mediated by the metal electrons and closely related to the concept of surface resistivity. Here we extend that theory to lower frequencies; for parallel adsorbate vibrations the theory predicts an anti-absorption resonance with an unique asymmetry which only depends on the ratio ω01 between the adsorbate vibrational frequency ω0 and ω1 = vF/δ where vF is the Fermi velocity and δ = cp the skin depth. The theory is in very good agreement with the IRAS measurements of Hirschmugl et al. [Phys. Rev. Lett. 65 (1990) 480] for CO on Cu(100) and in qualitative agreement with the measurements of Lin et al. [Phys. Rev. B 48 (1993) 2791] for CO on Ni(100).  相似文献   

20.
A new closed-form formulation of the statistical exciton model which gives results very similar to the total pre-equilibrium spectrum obtained by solving a set of Boltzmann-like master equations that describe the nuclear equilibration process, is suggested. The effect of including the loss of strength from each exciton state of a composite nucleus due to the transitions of Δn = 0 (Δp = Δh = 0) in both the master equations and closed-form formalisms is discussed.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号