共查询到20条相似文献,搜索用时 15 毫秒
1.
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
2.
D.S.C. Yee W.B. Stewart C.A. McDowell C.E. Brion 《Journal of Electron Spectroscopy and Related Phenomena》1975,7(2):93-117
A high resolution electrostatic electron analyser has been used to study Penning ionization electron spectra of H2, HD, D2, N2, CO, NO and O2 using helium metastable atoms (21S, 23S). Results for H2, N2 and CO are in good agreement with other work. New data are presented for HD, D2, NO and O2. The Penning electron spectra are also compared to the 584 Å photoelectron spectra obtained in the same apparatus. The relative vibrational intensifies for the given electronic bands indicate that in most cases Franck—Condon factors for Penning ionization and photoionization are very similar. However for the O2+(X2Πg) band, the (23S) Penning electron and photoelectron spectra show significant differences in the Franck—Condon envelopes This perturbation of the envelope for the Penning ionization may be explained by a competing autoionization process. The relative electronic transition probabilities are in many cases found to be different for Penning ionization and photoionization. 相似文献
3.
The electron spectra resulting from thermal collisions of He*(21S, 23S) metastable atoms with HCHO, CH3CHO, CH3COCH3, HCOOH and CH3COOH, are compared to the respective 584-Å photoelectron spectra. An analysis of the Penning electron band shape and the position of the peak maximum for the ground-state ions suggest there are significant differences in the Franck-Condon factors when compared with photoelectron spectra. This may be ascribed to modifications of the target potential-energy surfaces. It is also observed that the relative populations of the ionic states differ appreciably for Penning ionization and photoionization. 相似文献
4.
The He*(21S, 23S) Penning ionization electron spectra of HCN, (CN)2, CH3CN, BrCN and ICN are compared to the corresponding 584 Å photoelectron spectra. Large differences are observed for the relative populations of the ionic states of the various molecules when Penning ionization is compared to photoionization. For these molecules, the ratio of the normalized relative populations of states corresponding to removal of π bonding and nitrogen lone pair electrons is significantly greater for 584 Å photoionization than for He*(23S) Penning ionization. Some unidentified chemi-ionization processes are observed for (CN)2, BrCN and ICN. 相似文献
5.
D.S.C. Yee A. Hamnett C.E. Brion 《Journal of Electron Spectroscopy and Related Phenomena》1976,8(4):291-312
The Penning electron spectra of water, methanol, ethanol, isopropyl alcohol, tertiary butyl alcohol, dimethyl ether, ethylene oxide, diethyl ether, tetrahydrofuran and 1,4 dioxane, obtained using helium metastable atoms (21S, 23S), are compared to their respective photoelectron spectra at 584 Å. An analysis of the Penning electron band shape and the position of the peak maximum for the ground state ions suggest significant changes in the Franck—Condon factors in comparison with photoelectron spectra. This may be ascribed to modifications of the target potential energy curves. It is also observed that the relative populations of the ionic states differ appreciably for Penning ionization and photoionization. 相似文献
6.
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
7.
A nitrogen-pumped tunable dye laser is used as a spectrometer. It is especially well suited for spectral profile study of absorption lines starting from short-lived atomic levels. Up to now, in order to illustrate its feasibility, we have measured absorption profiles for the lines 4047 Å (73S1 ← 63P0) and 4358 Å (73S1 ← 63P1) of mercury. 相似文献
8.
Ionizing collisions of long lived excited particles with atoms and molecules are studied by a cross beam technique. For the first time reactions of atoms in high Rydberg states are included in the investigation. In this paper we report relative cross sections for the production of the ions RH+, RH 2 + , and H 2 + by collisions of excited rare gas atoms R* with H2. With HD as the target molecule the isotope effect for the production of RD+ and RH+ has been determined. In the case of argon and krypton, ions are produced only by the high Rydberg states, whereas in the case of helium and neon only the metastable states contribute to a measurable extent. The data indicate, that the reaction mechanism is different in principle for metastable and highly excited atoms. Simple models are proposed to explain the experimental results. 相似文献
9.
From a He-beam excited by electron impact we eliminated the He(21 S) component to better than 0.5% by irradiating light from a He discharge. The quenching process ishv(21 P→21 S)+He(21 S)→He(21 P)→He(11 S +hv) (21 P 1)1 S. By measuring the ions produced in collisions of the He-metastables with various target gases in a mass spectrometer, singlet to triplet Penning-cross section ratios were obtained. These ratios are without exception close to one, which is taken as evidence for the previously proposed electron exchange mechanism of the Penning ionization. In the case that more ions are produced in the collision of He (21 S) and He(23 S) with a target gas, separate relative production cross sections are obtained for the two metastables. For the rare gases the measurements are performed at two temperatures of the He-beam, 320 and 90 °K. It is found that the cross section ratio of associative — to Penning ionization increases considerably as the temperature is decreased for both, He(21 S) and He(23 S), the effect being much more pronounced for He(21 S). The results of this work are found to confirm conclusions drawn from measured energy distributions of the electrons ejected in the Penning process. 相似文献
10.
Penning electron distributions arising from the ionization of Na and K by He (1s 2s 1,3 S)-metastables in thermal collisions, as well as the absolute cross section for Penning ionization of Na by He (23 S) and relative cross sections for ionization of Na and K by He(21 S) and He(23 S) are measured. It is shown that under fairly general conditions the well depth ε* of the interaction potential between the metastable and the target particle can be obtained directly from the measured electron distributions. ε*-values are reported for the moleules He(1s 2s 1,3 S)-Na(2 S), K(2 S) (2,2Ω), and for He(1s 2s 1,3 S)-Hg(1 S)(1,3Ω). These latter values are obtained from previously published measurements and are to be considered preliminary. Further, additional evidence is given, that Penning ionization with metastables is an electron exchange process. 相似文献
11.
C.E. Briom C.A. McDowell W.B. Stewart 《Journal of Electron Spectroscopy and Related Phenomena》1973,1(2):113-130
A study has been made of the Penning ionization electron spectra resulting from collisions between rare gas atoms and helium metastable atoms. The results are compared and contrasted with photoelectron spectra at 584 Å. Additional bands appear in the electron spectra and are explained on the basis of fast neutral-neutral collisions involving curve crossing mechanisms. Electron spectra from mixed rare gas systems at higher pressures are examined. 相似文献
12.
《Surface science》2002,496(1-2):84-94
We have developed a new two-center close-coupling approach in which the time-dependent Schrödinger equation is solved for an active electron interacting with a slow projectile and a metal surface. The motion of the active electron in the metal subspace is discretized by using Weyl wave packets. Results for the time evolution of the atomic and metallic population amplitudes for the H/Al system are shown and discussed. 相似文献
13.
V. Čermák 《Journal of Electron Spectroscopy and Related Phenomena》1975,6(2):135-144
The autoionizing atomic states are obtained in dissociation Of O2, Cl2 and Br2 molecules excited by either fast neutral He atoms (O2) or by photons with 21.217 eV energy (Cl2, and Br2). Tentative assignment of the autoionizing levels is given for Cl* and for Br* atoms, and a more detailed one for O* atoms. 相似文献
14.
Kai Siegbahn 《Journal of Electron Spectroscopy and Related Phenomena》1985,36(2):113-129
A discussion of factors related to improved resolution in electron Spectroscopy for different modes of excitation is given. Some examples are presented from recent studies of solids, gases and liquids, together with some aspects on angular distributions. A new type of time-of-flight instrument is described where the electrons drift in a strong magnetic field with a dependence. A ‘modular’ instrument for different modes of excitation of gases, liquids and solids is presented. A symbiosis of ESCA and lasers concerns studies of excited or fragment molecules (free radicals) and excited surfaces. 相似文献
15.
《中国物理 B》2020,(1)
The electron capture processes in collisions of Li~(3+)ion with Li(1s~22s)and Li(1s~22p_(0,1))are investigated by using the two-center atomic orbital close-coupling method in the energy range from 0.1 keV/u to 300 keV/u.The interaction of the active electrons with the target ion is represented by a model potential.The present results for the Li~(3+)–Li(1s~22s)system are compared with the available theoretical data and general agreement is obtained for the high collision energies.It is also found that the total and partial electron capture cross sections are sensitive to the initial charge cloud alignment in the low energy region. 相似文献
16.
A theoretical treatment of the collisional ionization of a highly excited atom with a molecule is improved by use of the exact form factor of the hydrogen atom in highly excited states. The present treatment is still based on the previously proposed mechanism in which the Rydberg electron is ionized by gain of energy from rotational de-excitation of the molecule in a rotationally excited state. Closer comparison of experiment with theory is made for symmetric- as well as asymmetric-top molecules. 相似文献
17.
We report on high-resolution spectroscopy with two different samples of calcium atoms, in a laser-cooled and deflected beam and in a magneto-optical trap. The atomic beam was excited by spatially separated laser fields. For spectroscopy with stored atoms in a magneto-optical trap we used a multiple-pulse excitation scheme. The resolution as low as 2.5 kHz was limited by residual frequency fluctuations of our dye-laser spectrometer. The results should allow to establish a frequency standard with a relative uncertainty below 10–14. 相似文献
18.
Deexcitation of metastable He1 21S (excitation energy E1 = 20.6 eV) or 23S (E* =19.8 eV) atoms at a clean Pd(110) surface proceeds through a two-stage process (resonance ionization + Auger neutralization, RI + AN). The measured electron energy distribution reflects the self-convolution of the local density of states of the outmost atomic layer. A CO adlayer suppresses the RI step and the spectra are caused by Auger deexcitation (Penning ionization). Comparison with corresponding UPS data allows identification of the valence orbitals of the adsorbate. Emission up to the Fermi level is ascribed to contributions from the 5σ level. The effectively available excitation energy in front of the adlayer is lowered by 0.5 eV. Extensive data on the variation of the intensities from the adsorbate valence levels with angle of incidence as well as of emission are presented and are analyzed in terms of an empirical model. 相似文献
19.
A. B. Fedotov O. S. Ilyasov N. I. Koroteev A. M. Zheltikov 《Il Nuovo Cimento D》1992,14(10):1003-1013
Summary The experimental results on four-wave Raman and hyper-Raman scattering in a laser-produced and electric-discharge plasma are
presented. It has been shown that in spectra of four-wave mixing processes resonances appear due to the Raman and hyper-Raman
scattering on atomic and ionic excited states. The temporal behaviour of the scattered-signal intensity has been found to
be connected with the population relaxation of atomic and ionic excited states. We have observed for the first time the resonance
in the spectrum of coherent hyper-Raman scattering in electric-discharge plasma associated with the electron transition between
the excited and autoionizing state of a copper atom.
Paper presented at the ?XI European CARS Workshop?, Florence, Italy, 23–25 March, 1992. 相似文献