排序方式: 共有130条查询结果,搜索用时 15 毫秒
51.
M. Galiová J. Kaiser K. Novotný J. Novotný T. Vaculovič M. Liška R. Malina K. Stejskal V. Adam R. Kizek 《Applied Physics A: Materials Science & Processing》2008,93(4):917-922
Single-pulse Laser-Induced Breakdown Spectroscopy (LIBS) and Laser-Ablation Inductively Coupled Plasma Mass-Spectrometry (LA-ICP-MS)
were applied for mapping the silver and copper distribution in Helianthus Annuus L. samples treated with contaminant in controlled conditions. For Ag and Cu detection the 328.07 nm Ag(I) and 324.75 nm Cu(I)
lines were used, respectively. The LIBS experimental conditions (mainly the laser energy and the observation window) were
optimized in order to avoid self-absorption effect in the measured spectra. In the LA-ICP-MS analysis the Ag 107 and Cu 63
isotopes were detected. The capability of these two analytical techniques for high-resolution mapping of selected trace chemical
elements was demonstrated. 相似文献
52.
C.M. Dion O. Dulieu D. Comparat W. de Souza Melo N. Vanhaecke P. Pillet R. Beuc S. Milošević G. Pichler 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2002,18(3):365-370
We present the results of absorption measurements in a cesium vapor around 630 K, together with photoionization spectra through
a resonance-enhanced two-photon absorption of ultracold cesium dimers created after photoassociation of ultracold cesium atoms.
The maximum efficiency of the ultracold molecule ionization is found for wavelengths where absorption at thermal energies
is the strongest, in agreement with our theoretical simulations of both processes, involving the so-called Cs2 diffuse bands. This result will be helpful for further optimization of such a direct way of detection of ultracold molecules.
Received 13 September 2001 相似文献
53.
A. V. Golovin N. A. Cherepkov V. V. Kuznetsov 《Zeitschrift für Physik D Atoms, Molecules and Clusters》1992,24(4):371-375
Use of a coincidence technique for registration of fragment ions and photoelectroms from dissociative ionization of molecules opens the possibility of studying the photoionization of oriented molecules in a gas phase. The first results obtained by this technique for O2 molecules are presented. The angular distribution of photoelectrons as a function of an angle between molecular axis and a photoelectron momentum is measured for theB
2
g
–
final ionic state using the HeI resonance radiation. From measured data it follows that the ratio of channel cross sections is /=0.67±0.08. 相似文献
54.
55.
Using rate equations the effect of different pulse sequences, pulse durations, and delay times of two lasers on ionization probability and selectivity in resonant two-step photoionization of molecules is investigated. The results demonstrate to what extent a given selectivity of the absorption or relaxation of the intermediate electronic, state is influenced by a special combination of these parameters. 相似文献
56.
Gerhard Walder Keith W. Kennedy Olof Echt 《Zeitschrift für Physik D Atoms, Molecules and Clusters》1993,26(Z1):288-290
We investigate the time dependence of carbon cluster ions, formed via thermionic emission from photoexcited fullerenes (C60 and C70). By pulsing the extraction field, we are able to observe delayed ions formed as late as 100 µs after excitation at 532 nm, 355 nm, or 266 nm. All even-sized clusters in the range 36 n 70 undergo thermionic emission. 相似文献
57.
Gil Jae Park 《Journal of luminescence》2004,106(2):103-108
The femtosecond laser was used to irradiate sol-gel derived Sm3+-doped Al2O3-SiO2 glasses, in which the Sm3+ was reduced into Sm2+ ions. The fluorescence line narrowing was applied to investigate the coordination sphere of the Sm2+ ion. The spectral hole burning was performed on 7F0→5D0 transition of the Sm2+. The depth and width of the burnt holes were ∼27% and ∼4 cm−1 FWHM at 7 K, respectively. Hole spectra were stable up to room temperature. The hole-burning efficiency was superior to that of Sm2+ in H2 treated glasses and comparable to that in X-ray in terms of hole-burning dynamics. 相似文献
58.
K. Johst 《Applied physics. B, Lasers and optics》1991,53(1):46-51
Using the time-dependent Schrödinger equation we investigate the effect of different pulse sequences of two lasers on selective ionization in three-level systems driven by coherent radiation fields. It is assumed that inhomogeneous broadening as well as the radiative decay can be neglected during the laser pulses. We demonstrate to what an extent the selectivity given by the absorption or relaxation process can be increased by coherent interaction during the first step and different timing of the incoherent interaction during the second step of a two-step photoionization. A comparison is made with the rate-equation results. We could show that utilization of coherent excitation for high ionization selectivity is most efficient if the two laser pulses do not overlap. 相似文献
59.
Accepted: 6 March 1997 相似文献
60.