磁脉冲压缩器在卤化铜激光器上的应用

在卤化铜激光器脉冲放电电源系统中，为减轻闸流管的工作负担并同时保证电路的快放电激励，采用了单级磁脉冲压缩器.分析了磁脉冲压缩器的工作机理，介绍了所采用磁脉冲压缩器的设计考虑及参数选用. 关键词： 磁脉冲压缩器 闸流管 CuBr激光器     

Macroscopic theory of activated decay of metastable states

The Brownian motion of a particle over a potential barrier, a problem first solved by Kramers, is reexamined also for the case of intermediate friction, to which Kramers' solutions do not apply. The theory is macroscopic and entirely based on the Langevin equation of the particle, but it makes essential use of ideas of a recent microscopic theory of Grabert and of Pollak, Grabert, and Hänggi for a particle coupled to an infinite set of harmonic oscillators. Their result for the escape rate is recovered, but the present method seems more generally applicable. We introduce and use a new theoretical tool-the transformation to a new set of variables mixing the macroscopic and the noise variables of the Langevin equation.     

Theory of the decay process of metastable state

The short-time and long-time behavior of the distribution function P(x, t) are investigated in the laser model by using the generating function $\text{G(α,}\text{β}\text{;t) = σ(α-y(t)) Π}{}^{\mathrm{\infty }}{}_{\mathrm{n=2}}\text{σ(β}{}_{\mathrm{n}}\text{- M}{}_{\mathrm{n}}\text{(t)),}\text{where}\text{y(t)  ?xP(x, t)}\text{d}\text{x}\text{and}\text{M}{}_{\mathrm{n}}\text{(t)  ?(x - y(t))}{}^{\mathrm{n}}\text{P(x,t)}\text{d}\text{x}$.     

On the stimulated radiative decay of metastable states

I discuss the possibility of observing stimulated gamma emission by direct transition from long-lived metastable states of isomer nuclei, considering the effects of surplus emission-line broadening, so-called “laser lethargy,” and so on. A scenario and the configuration of an eventual experiment are presented.     

Chemical ionization of hydrogen halide molecules in collision with metastable helium atoms

An anomaly of the temperature dependence of the cross section for chemical ionization of HBr molecules by metastable helium atoms He*(2³ S ₁) is discovered. It is shown that the interaction anisotropy induced by rotation of the HBr molecule has a significant influence on the formation of the anomaly. Zh. Tekh. Fiz. 68, 13–15 (February 1998)     

Structure of copper halide nanocrystals in photochromic glasses

The crystal structure of CuCl nanocrystals with effective radii ranging from 2.4 to 18.5 nm in photochromic glasses heat treated under different conditions is investigated using exciton spectroscopy, x-ray powder diffraction, and small-angle x-ray scattering. It is revealed that the size dependence of the energy of the Z ₃ exciton exhibits an anomalous behavior. The results obtained suggest that small-sized CuCl nanocrystals can crystallize in a modification different from the stable cubic modification.     

Isotope effects in the metastable decay of Ne2 +

Neon dimer ions undergo spontaneous dissociation (metastable decay) several microseconds after formation by electron impact ionization of neon clusters. In this contribution we compare the kinetic energy release distribution (KERD) of the previously reported isotopomer ²⁰Ne₂ ⁺ with that of ²²Ne₂ ⁺. The heavy isotopomer shows the same two components in the KERD as the lighter ones. However, the high-energy component that is due to electronic pre-dissociation is reduced in intensity. The decrease is attributed to a reduced predissociation rate from the II(1/2u) state into I(3/2u).     

Investigation of the photoelectron decay of silver halide microcrystal

The microwave absorption dielectric spectrum can be used to study the decay process of free photoelectrons and shallow-trapped electrons in semiconductor crystals. The decay curve of free photoelectrons and shallow-trapped electrons of silver halide grains is measured using this technique. The influence of iodide and K_4Fe(CN)_6 shallow electron trap dopants on the photoelectron lifetime of silver halide grains is studied. For the unsensitized cubic AgCl crystals, when the free photoelectron lifetime (FLT) reaches a maximum, the photographic efficiency is optimal. From our analysis, we conclude that FLT is the longest for the cubic AgCl crystals doped with 0.5% iodide at 80% doping position and 1×10^{-6} mol K_4Fe(CN)_6/molAg, whereas, for the highly photosensitized cubic AgBrCl crystals doped with K_4Fe(CN)_6, the photographic efficiency is optimal when the FLT reaches its minimum. The free photoelectron lifetime reaches minimum and the sensitivity of AgBrCl emulsion reaches maximum when the doping position is 30%Ag at K_4Fe(CN)_6 content of 10^{-6}mol/molAg.     

Radiative decay of the metastable quartet state of copperporphin

In CuP the low temperature luminescence originates from eight transitions between a quartet (M = ±3/2, ±1/2) and a doublet (M′ = ±1/2) with M and M′ denoting the (approximate) eigenvalues of the spin angular momentum S_z along the fourfold axis. Here we report (1) the selection rules governing the polarizations of the transitions; (2) the zero-field splitting ξ between the ±3/2 and ±1/2 components of the quartet for CuP in an n-octane crystal (ξ = 1·1 ± 0·2 cm^-1); (3) a photo-selection experiment on CuP in an isopentane glass from which it is concluded that the ratio of in-plane to out-of-plane polarization in the 0-0 band at 2·1 K amounts to an intensity ratio I _‖/I _⊥ ≈ 2. The implications of these results for the different SOC pathways are analysed.     

半导体泵浦射流型亚稳态氩激光国际首次出光北大核心CSCD

半导体泵浦亚稳态惰性原子激光是高能光泵浦气体激光领域具有潜力的新方案。已有报道均在约束的放电空间内产生亚稳态原子,功率放大受到多因素制约。为突破现有方案的局限,采用大气压等离子体射流方式在羽流区域产生高浓度亚稳态氩原子(1014 cm^(−3)量级),将放电和激光区域空间分离,利用811 nm窄线宽半导体激光器作为泵浦源,基于泵浦、激光和气流相互垂直的结构实现912 nm激光输出,有效拓展了该型激光体系的功率定标放大能力。     

The pumping efficiency of copper halide lasers

A simple relation between the copper halide laser output and the densities of ground state (²S) and metastable state (²D) copper atoms was found. This relation was used to analyze the experimental results of Nerheim. In all the analyzed systems it was found that about four percent of the ground state copper atoms take part in the lasing process. This may have implications for the efficiency of copper halide lasers.     

Stabilized high-temperature hexagonal phase in copper halide nanocrystals

Low-temperature (T = 4.2–77 K) absorption spectra of CuCl and CuBr nanocrystals in photochromic glass matrixes are studied. A fine structure of exciton absorption bands (Z₃ band for CuCl and Z₁₂ band for CuBr) is discovered and studied as a function of nanocrystal size. It is suggested that the high-energy part of the absorption band is due to the high-temperature hexagonal β phase being stabilized in very small samples; a transition to the stable cubic phase with increasing nanocrystal size is demonstrated.     

Instability and metastable chaos in dual-mode laser

Tashkent State University. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 34, pp. 1061–1064, September, 1991.     

Pion decay site spectroscopy in copper

With the aim of obtaining direct information on the sites occupied by positive pions (π⁺), channelling experiments have been performed on the decay muons (μ⁺) from π⁺ implanted into high-purity copper crystals. At 100 K virtually exclusive occupancy of octahedral interstitial sites (0) is found in good accordance with earlier μSR results. At room temperature a significant fraction of the implanted pions decay on metastable tetrahedral interstitial sites (T). The data suggest strongly that above about 100 K both μ⁺ and π⁺ diffuse by phonon-assisted tunnelling between stable 0 sites and metastable T sites. The enthalpy difference between these two sites is estimated to be about 50 meV for μ⁺ and of the same order of magnitude for π⁺. These values are much smaller than the available theoretical predictions. The implications of low-lying metastable interstitial sites for the μ⁺ stopping sites of low temperatures are discussed.     

Signal enhancement in laser spectroscopy of metastable states

A two laser excitation scheme has been applied to Ca atoms in an atomic beam. It permits to transfer narrow Doppler-free signals from a weak transition into a strong resonance line. This leads to a large increase of the signal-to-noise ratio and is of relevance for the application of the Ca intercombination transition as a possible new standard in the optical range.     

Enhancement of activated decay of metastable states by resonant pumping

We consider the effect of a high-frequency pumping cost on the escape rate of a classical underdamped Brownian particle out of a deep potential well. The energy dependence of the oscillation frequency(E) is assumed to be weak on the scale of thermal energy,_E(0)T(0)T/V₀ (0)[_E(0) is the derivative of(E) atE= 0,V ₀ is the barrier height,V ₀ T]. The quadratic-in- contribution to the decay rate is calculated in two different regimes: (1) for the case of resonance of the pumping frequency with the nth harmonic of the internal motion at an energye, when = n(e); (2) for a rollout region of the basic resonance near the bottom of the potential well, when ¦-(0)¦ and is the damping coefficient. In the latter case the absorption spectrum and the enhancement of the decay rate are calculated as functions of two reduced parameters, the anharmonicity of the potential,v _E (0)T/, and the resonance mismatch, [ —(0)]/. It is shown that the effect of the pumping increases with diminishing ¦v¦ and at small v is proportional tov ^–1. In this regime, the dependence on is stepwise: the pumping contribution is large for v > 0 and small for v < 0. In the frame of our theory, the decay rate is invariant against the simultaneous alternation of the signs of andv. The spectrum of the energy absorption has the standard Lorentzian shape in the absence of anharmonicity,v=0, and with increasing of ¦v¦ shifts and widens retaining its bell-shape form.     

Resonances,metastable states and exponential decay laws in perturbation theory

Resonances which appear as perturbed bound states are discussed in the framework of Balslev-Combes theory. The corresponding metastable states are constructed using the formal perturbation expansion to orderN–1 for the (nonexistent) perturbed bound states. They are shown to have exponential decay in time governed by the complex resonance energies, up to a background of order 2N in the perturbation parameter. The results apply in lowest orderN=1 to the perturbation of bound states embedded in the continuum and in arbitrary order to cases like the Stark effect.Dedicated to Res Jost and Arthur Wightman