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1.
We have performed extensive numerical studies of Coulomb explosion of small molecules such as CO2 and N2O with the help of a hydrodynamic model, which allows one to deal with many-electron systems in intense laser fields. The predicted kinetic energy releases of the fragmentation channels are in good agreement with the measured energies, using realistic molecular and laser excitation condition parameters. 相似文献
2.
V. V. Gridchin A. M. Popov O. V. Smirnova 《Journal of Experimental and Theoretical Physics》2001,93(2):295-300
The angular distributions of the fragments from a Coulomb explosion of a diatomic heteronuclear molecule during multielectron dissociative ionization in a superintense field are considered in terms of classical mechanics. The patterns of angular distributions of the Coulomb explosion fragments are shown to differ in different ranges of laser pulse parameters. In particular, there are two distinct modes of fragment separation: separation in a Coulomb field and separation in the field of an effective “fragment + field” potential. The effective potential includes both the force of Coulomb repulsion between the fragments and the period-averaged force exerted on the system by the field; it can be determined by using the Kramers-Henneberger method. The limits of applicability of the Kramers-Henneberger method to the problem in question are discussed. These limits specify the range of field parameters in which the fragments fly apart in a direction perpendicular to the field for the initially arbitrary orientation of the molecular axis relative to the field. 相似文献
3.
C. Rösel F. F. Karpeshin P. David H. Hänscheid J. Konijn C. T. A. M. de Laat H. Paganetti F. Risse B. Sabirov L. A. Schaller L. Schellenberg W. Schrieder A. Taal 《Zeitschrift für Physik A Hadrons and Nuclei》1993,345(4):425-426
In the spectrum of muonic X-rays of238U measured in coincidence with prompt fission events a structure has been found which is attributed to 2p1s transitions of the muon attached to heavy fragments. The intensityI
s of this structure relative to the strengthI
pf observed for prompt fission has been determined to beI
s/I
pf=(6.0± 2.1) %. Although the experimental significance for the appeareance of this phenomenon is weak, this is the first experimental indication for its occuxence.We are indebted to the following institutes or organizations for financial support: Bundesministerium für Forschung und Technologie der Bundesrepublik Deutschland contract number 06BN271 (CR,PD,HH,FR,WS), Foundation for Fundamental Research on Matter (FOM) and the Netherlands Organization of the Advancement of Pure Research (NWO) (JK,CTAMdL,AT), the Swiss National Foundation (SNF) (LAS,LS), and the Heinrich-Hertz-Foundation (HH) (FFK,BS). 相似文献
4.
Coulomb explosion of a metal exposed to an intense picosecond laser pulse is numerically simulated using a plasma layer as an example. It is shown that plasma electrons leave the plasma layer under the action of the ponderomotive force opposing the laser radiation field gradient, whereas plasma ions fly away in the field of the self-space charge. 相似文献
5.
The nonlinear problem of the expansion of a uniform spherical cluster, which consists of ions with a charge sufficient to
accelerate relativistic energies has been solved precisely. It has been shown that relativistic non-linearity is responsible
for the formation of an expanding shell-type structure. The space-time and energy characteristics of the relativistically
exploding cluster have been found. 相似文献
6.
T. Okada M. Maeda Y. Kajiki K. Muraoka M. Akazaki 《Applied physics. B, Lasers and optics》1987,43(2):113-116
The sensitive detection of H2 molecules was demonstrated by means of twophoton excited laser-induces fluorescence spectroscopy with a narrow-band ArF excimer laser. A detection limit of 2×1014 cm–3 was obtained with an excitation power of 150 kW. This is already comparable with that obtained by the coherent anti-Stokes Raman scattering (CARS). This technique was successfully applied to measure a spatial distribution of H2 in a town-gas burner. 相似文献
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8.
C. Caraby L. Adoui J.P. Grandin A. Cassimi 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》1998,2(1):53-56
We report the observation of resonances in the intensity correlation spectra of a 3D rubidium optical lattice, which we attribute
to light scattering from propagating atomic density fluctuations in the lattice. This process is the spontaneous analog of
the stimulated scattering mechanism recently described by Courtois et al.. We investigate the dependence of the new resonances on the lattice angle and show that they disappear for large angles,
thus resolving previous discrepancies on the subject.
Received: 30 January 1997 / Accepted: 9 October 1997 相似文献
9.
The mechanism of the Coulomb explosion of a metal in an external pulsed electric field is discussed. In the case of a low-frequency field, when its frequency is lower than the frequency of electron collisions, it is impossible to reach the conditions of the Coulomb explosion of a metal if the field pulse duration is shorter than the time of electron energy relaxation upon elastic collisions, and the electron temperature is well above the Fermi energy and the work function. In the case of a high-frequency field, e.g., in a powerful pulse of ultraviolet laser radiation, the Coulomb explosion can occur if the field strength is well above the intraatomic field strength (i.e., when the laser power density is ≥1019 W/cm2). 相似文献
10.
DJ Smith KW Ledingham RP Singhal T McCanny P Graham HS Kilic P Tzallas C Kosmidis AJ Langley PF Taday 《Rapid communications in mass spectrometry : RCM》1999,13(14):1366-1373
With the development of high intensity femtosecond lasers, the ionisation and dissociation dynamics of molecules has become an area of considerable interest. Using the technique of femtosecond laser mass spectrometry (FLMS), the molecules carbon disulphide, pyrimidine, toluene, cyclohexanone and benzaldehyde are studied with pulse widths of 50 fs in the near infrared (IR) wavelength region (790 nm). Results are presented and contrasted for laser beam intensities around 10(15) and 10(16) W cm(-2). For the lower intensities, the mass spectra yield dominant singly charged parent ions. Additionally, the appearance of doubly charged parent ions is evident for carbon disulphide, toluene and benzaldehyde with envelopes of doubly charged satellite species existing in these local regions. Carbon disulphide also reveals a small triply charged component. Such atomic-like features are thought to be a strong fingerprint of FLMS at these intensities. However, upon increasing the laser intensity to approximately 10(16) W cm(-2), parent ion dominance decreases and the appearance of multiply charged atomic species occurs, particularly carbon. This phenomenon has been attributed to Coulomb explosions in which the fast absorption of many photons may produce transient highly ionised parent species which can subsequently blow apart. Copyright 1999 John Wiley & Sons, Ltd. 相似文献
11.
Raciti G Cardella G De Napoli M Rapisarda E Amorini F Sfienti C 《Physical review letters》2008,100(19):192503
Two-proton decay from (18)Ne excited states has been studied by complete kinematical reconstruction of the decay products. The (18)Ne nucleus has been produced as a radioactive beam by (20)Ne primary projectile fragmentation at 45 AMeV incident energy on a Be target. The (18)Ne at 33 AMeV incident energy has been excited via Coulomb excitation on a (nat)Pb target. The obtained results unambiguously show that the 6.15 MeV (18)Ne state two-proton decay proceeds through a (2)He diproton resonance (31%) and democratic or virtual sequential decay (69%). The quoted branching ratio has been deduced from relative angle and momentum correlations of the emitted proton pairs. 相似文献
12.
13.
Siems T Anagnostopoulos DF Borchert G Gotta D Hauser P Kirch K Simons LM El-Khoury P Indelicato P Augsburger M Chatellard D Egger J 《Physical review letters》2000,84(20):4573-4576
A Doppler broadening of x-ray transitions from pionic nitrogen and muonic oxygen, which is attributed to Coulomb explosion of the molecules, has been observed by using a crystal spectrometer. Large linewidths indicate fast ionization of the molecules and a charge of (3-4)e for the accelerated fragments. 相似文献
14.
When femtosecond laser irradiates materials, plasma with high electronic temperature and low lattice temperature will form due to very high laser power density. This plasma with high electronic temperature cannot exist stably, and it has a trend to expand. If the plasma inclusion is initialized, it will be confined by outer layers when it expands. In this paper, the energy conservation rule was used to analyze the mechanical evolution of inclusion of plasma explosion. An inequality for judging whether the film can be damaged has been deduced. 相似文献
15.
C. Cornaggia 《Laser Physics》2009,19(8):1660-1670
Multiple ionization of small molecules leads to multifragmentation called Coulomb explosion. The atomic positions prior to the fragmentation event are determined from the multicharged fragments trajectories. Following the pioneering contribution of Prof. N.B. Delone on atomic ionization using strong laser fields, intense femtosecond laser pulses in the 1015 W cm?2 range permit an efficient removal of valence electrons. Pulse durations have to be reduced to a few cycles in order to avoid any significant molecular stretching during multiple ionization. Pumpprobe excitation schemes offer promising perspectives for straightforward ultrafast Coulomb explosion imaging of excited and ionized molecular species. 相似文献
16.
17.
《Physics letters. A》1968,28(3):205-206
The 3Π0 state of in CC14 forms a hole injecting contact to anthracene crystals with a mean free path √Dτ in solution of (3 ± 2) × 10−6 cm. 相似文献
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19.
A. J. Cole A. Chabane M. Charvet P. Désesquelles A. Giorni D. Heuer A. Lleres J. B. Viano 《Zeitschrift für Physik A Hadrons and Nuclei》1995,353(3):279-287
We present an analysis which aims at explaining the similarities (and differences) which exist between a simple bond percolation process on a cubic lattice and the fragmentation of highly excited atomic nuclei. Emphasis is placed on discussing percolation in terms of concepts which are well known in nuclear physics such asQ-value and particle emission thresholds. Similarities and differences between the bond percolation process and nuclear fragmentation are discussed. An approximate expression for the microcanonical partition sum (number of microstates) corresponding to any given percolation partition is shown to provide a good starting point for predicting fragment size distributions.Communicated by: X. Campi 相似文献
20.
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