共查询到20条相似文献,搜索用时 0 毫秒
1.
V.S. Kushawaha 《Journal of Quantitative Spectroscopy & Radiative Transfer》1985,34(3):305-308
A combination of cw and pulsed dye lasers has been used to study the competition between fluorescence and associative ionization involving excited and ground-state Na. An associative ionization cross-section for principal quantum numbers n > 14 has been estimated to be more than 102 Å2. 相似文献
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Electron spectra resulting from collisions of thermal 23S metastable helium atoms with HF, HCl, HBr and HI are compared with the respective 584 相似文献
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Coherent control techniques are computationally applied to cold (1 mK相似文献
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We report on a study of time dependence of ir laser emission at 3.41 μm in a dense Na vapor that is resonantly excited to the 32 P levels by a flashlamp, pumped dye laser. Energy-pooling collisions (excitation transfer) between excited atoms create a large population inversion among the 52 S 1/2 and 42 P 3/2 states which is destroyed by electron collisions as a result of subsequent plasma formation. The ir laser emission may serve as a new diagnostic tool to follow the time evolution of such media. 相似文献
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We present a time-resolved experimental study of ionization by superelastic collisions in excited strontium vapor. Using short duration laser pulses for resonant excitation, we clearly observe that a delay time is necessary to reach runaway collisional ionization after the end of laser excitation. 相似文献
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V. Čermák 《Journal of Electron Spectroscopy and Related Phenomena》1976,8(4):325-329
The electron spectroscopical determination of the primary distribution of vibrational levels of the HCl+ and HBr+ ions in the excited A2Σ+ states, formed in Penning ionization by helium metastables, has shown that the vibrational distribution determined by fluorescence measurement is altered by post-ionization relaxation effects. 相似文献
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Molecules in the source region of a time of flight mass spectrometer are ionized by ultraviolet laser radiation. Under certain conditions mass spectra consisting of a remarkably periodic set of ion peaks are generated. It is demonstrated that these result from spatially periodic ionization within the mass spectrometer which is a consequence of the development of standing electromagnetic waves. 相似文献
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In this paper we report on inner ionization of Xen clusters (n = 55-
2171) in ultraintense Gaussian laser fields (peak intensity I = 1015- 1020 Wcm-2, pulse width τ= 25 fs, frequency 0.35 fs-1). The cluster inner ionization process is induced by the barrier
suppression ionization (BSI) mechanism and by electron impact ionization
(EII), which occurs sequentially with the BSI. We address electron impact
ionization of clusters, which pertains to inelastic reactive processes of
the high-energy (100 eV–1 keV per electron) nanoplasma. We utilized
experimental data for the energy dependence of the electron impact
ionization cross-sections of Xej+ (j = 1-10) ions, which were fit by
an empirical three-parameter Lotz-type equation, to explore EII in clusters
by molecular dynamics simulations. Information was obtained on the yields
and time-resolved dynamics of the EII levels (i.e., number nimp of
electrons per cluster atom) in the Xen clusters and their dependence on
the laser intensity and cluster size. The relative long-time (t = 90 fs)
yields for EII, nimp/nii (where nii is the total inner
ionization yield) are rather low and increase with decreasing the laser
intensity. In the intensity range I = 1015-1016 Wcm-2,
nimp/nii = 0.21 for n = 2171 and nimp/nii = 0.09-0.14
for n = 459, while for I = 1018-1020 Wcm-2,
nimp/nii = 0.01-0.05. The difference Δnimp between
the EII yield at long time and at the termination of the laser pulse
reflects on ionization dynamics by the nanoplasma when the laser pulse is
switched off. For Xe2171 in the lower intensity domain, Δ
nimp = 0.9 at I = 1015 Wcm-2 and Δnimp = 0.4 at
1016 Wcm-2, reflecting on EII by the persistent nanoplasma under
“laser free” conditions, while in the higher intensity domain of I =
1017 - 1018 Wcm-2, Δnimp is negligibly small
due to the depletion of the transient nanoplasma. 相似文献
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Using helium metastable atoms (21S, 23S), the Penning ionization of C2H4 has been studied using a high resolution electrostatic electron analyzer. The Franck—Condon envelope for the ground state of C2H4+ (X2B3u) is found to be the same for He* (23S) Penning ionization and 584 Å photoionization. The ΔE shift values and the relative electronic transition probabilities are reported for four ionic states. Unusually large differences have been found for the relative electronic transition probabilities for Penning ionization and photoionization. 相似文献
17.
R. Khare 《Optics Communications》2010,283(4):542-546
The pulsed optogalvanic (OG) effect is used to observe Penning ionization in a Zr-Ne hollow-cathode discharge, which was axially irradiated by a pulsed dye laser pumped by copper vapor laser. The effect of discharge current on the temporal evolution of the OG signal is studied at 588.2, 594.5, 597.6 and 614.3 nm. The double humped temporal profile of the OG signals, corresponding to transitions of neon, and closeness of energy levels between that level of neon (Ne) and excited levels of zirconium (Zr) ions confirmed that Penning type of ionizing energy transfer collisions were taking place in the Zr-Ne discharge at lower discharge currents (≤5 mA). The disappearance of the double humped feature in the temporal profile of the OG signals indicated that the Penning contribution became negligible at higher discharge currents (≥10 mA). 相似文献
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HU Wei WANG Yansen FANG Dufei LU Fuquan TANG Jiayong YANG Fujia 《Chinese Journal of Lasers》1994,3(3):223-230
ElectronimpactionizationcrosssectionsforLi-likeAlioningroundandexcitedstatesHUWei;WANGYansen;FANGDufei;LUFuquan;TANGJiayong;Y... 相似文献
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Reinhard A Cubel Liebisch T Younge KC Berman PR Raithel G 《Physical review letters》2008,100(12):123007
In rubidium Rydberg states, the collision nD_(5/2)+nD_(5/2)-->(n-2)F_(7/2)+(n+2)P_(3/2) is nearly resonant in the vicinity of n=43. As a result, over a short range of n centered around n approximately 43 the Rydberg-Rydberg interaction potential is quite large and turns from repulsive to attractive [Phys. Rev. A 75, 032712 (2007)10.1103/PhysRevA.75.032712]. We use state-selective field ionization to investigate the effect of this resonance on instantaneous excitation of mixed two-particle states, state-mixing collisions, and Penning ionization. We find that these processes depend on the magnitude and sign of the two-particle interaction potential, and thus on n near the resonance. The large magnitude of the observed state mixing provides evidence for many-body effects. 相似文献
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We have observed electron impact ionization of highly excited sodium Rydberg atoms in ns and nd states, n=35-51, below E=2 eV electron kinetic energy with energy resolution 0.25 eV. Measured absolute cross sections near 0 eV range from sigma(35d) approximately 7 x 10(-10) to sigma(50d) approximately 4 x 10(-9) cm(2). The energy dependence is consistent with that of widely used binary encounter approximation cross sections, and sigma(n) follows a power law in n. The measured cross sections are 14 to 24 times larger than theoretically predicted values. This enhancement may signal the effect of large polarizabilities of high Rydberg states not yet accounted for in ionization theories. 相似文献