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Photoelectron angular distributions(PADs) from two-photon ionization of atoms in linearly polarized strong laser fields are obtained in accordance with the nonperturbative quantum scattering theory.We also study the influence of laser wavelength on PADs.For two-photon ionization very close to the ionization threshold,most of the ionized electrons are vertically ejected to the laser polarization.PADs from twophoton ionization of atoms are determined by the second order generalized phased Bessel function at which the ponderomotive parameter plays a key role.In terms of dependence of PADs on laser wavelength,corresponding variations for the ponderomotive parameter are demonstrated. 相似文献
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We report on the strong field ionization of small transition metal clusters (nickel, Ni(n) n=1-36) within the quasistatic regime at an infrared wavelength of 1.5 microm and at intensities up to 2 x 10(14) W/cm(2). From ion yields in a constant axial intensity beam, we obtained saturation intensities for the individual Ni(n) clusters. As compared to quasistatic, single active electron calculations, a dramatic suppression of ionization was observed. Dynamic polarization in the laser field likely leads to strong multielectron screening of the "active" electron. Representing the metal clusters as classical conducting spheres, we obtained, via a barrier suppression calculation, the classical ionization rates. Agreement was obtained for larger clusters with n>10 when the dynamic polarization was taken into account, emphasizing the multielectron nature of the ionization suppression. 相似文献
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We report on a systematic study of the laser polarization effect on a femtosecond laser filamentation in air.By changing the laser's ellipticity from linear polarization to circular polarization, the onset position of laser filament formation becomes farther from the focusing optics, the filament length is shorter, and less laser energy is deposited. The laser polarization effect on air filaments is supported by a simulation and analysis of the polarization-dependent critical power and ionization rates in air. 相似文献
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本文运用将含时密度泛函理论和分子动力学非绝热耦合的方法,研究了CO分子在不同强度、不同极化方向的激光场中的电离和动力学行为. 研究发现,激光强度越强,CO分子吸收的能量越多,电离越早且电离越强,CO分子键长变长且伸缩振动越剧烈. 此外,CO分子偶极矩的变化及峰值也随着激光强度的增强而增大. 对激光极化方向的研究发现,激光极化方向沿着CO分子轴向时,分子的电离最强且伸缩振动最剧烈. 当激光极化角增大时,CO分子的电离逐渐被抑制且电子的偶极振动对激光极化方向表现出较强的依赖性. 此外研究还表明,CO分子碳原子和氧原子周围电子的弥散方式不同且与激光极化方向有关.
关键词:
含时密度泛函理论
分子动力学
分子电离 相似文献
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G. Morello F. Della SalaL. Carbone L. MannaR. Cingolani M. De Giorgi 《Superlattices and Microstructures》2010
In this contribution we report on an optical nonlinearity featuring colloidal seeded grown CdSe/CdS nanorods (NRs). It consists of a photoluminescence (PL) blueshift of single rod spectra with increasing laser power and a transient, power-dependent redshift of the spectra studied by time resolved PL measurement, strictly related to the multicarrier scattering occurring at high excitation density. We attribute this nonlinearity to a photo-induced screening of an internal field, originating from the piezoelectric polarization induced at the core/shell interface. 相似文献
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Bhardwaj VR Simova E Rajeev PP Hnatovsky C Taylor RS Rayner DM Corkum PB 《Physical review letters》2006,96(5):057404
Linearly polarized femtosecond light pulses, focused inside fused silica to an intensity that leads to multiphoton ionization, produce arrayed planes of modified material having their normal parallel to the laser polarization. The planes are < or = 10 nm thick and are spaced at approximately lambda/2 in the medium for free space wavelengths of both 800 and 400 nm. By slowly scanning the sample under a fixed laser focus, order is maintained over macroscopic distances for all angles between the polarization and scan direction. With the laser polarization parallel to the scan direction we produce long-range Bragg-like gratings. We discuss how local field enhancement influences dielectric ionization, describe how this leads to nanoplane growth, why the planes are arrayed, and how long-range order is maintained. 相似文献
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Brixner T Krampert G Pfeifer T Selle R Gerber G Wollenhaupt M Graefe O Horn C Liese D Baumert T 《Physical review letters》2004,92(20):208301
We demonstrate that the use of time-dependent light polarization opens a new level of control over quantum systems. With potassium dimer molecules from a supersonic molecular beam, we show that a polarization-shaped laser pulse increases the ionization yield beyond that obtained with an optimally shaped linearly polarized laser pulse. This is due to the different multiphoton ionization pathways in K2 involving dipole transitions which favor different polarization directions of the exciting laser field. This experiment is a qualitative extension of quantum control mechanisms which opens up new directions giving access to the three-dimensional temporal response of molecular systems. 相似文献
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Abstract We studied the erbium-doped fiber laser transient behavior dependence on the pump polarization state or on the cavity polarization eigenvalues. Several series of measurements are shown in which the changes in the transient laser response can be appreciated as the pump polarization state, or the cavity polarization eigenvalues are modified by means of polarization controllers. Results are fitted to a model considering polarization hole burning. It is shown that including this effect is fundamental for a correct erbium-doped fiber laser transient model. On the other hand, the validity of the model's fitting parameters under pump or cavity polarization changes is analyzed. 相似文献
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Modulation of ionization on laser frequency in ultra-short pulse intense laser--gas-target
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Based on the dispersion relation of intense laser pulse propagating in gradually
ionized plasma, this paper discusses the frequency modulation induced by ionization
of an ultra-short intense laser pulse interacting with a gas target. The
relationship between the frequency modulation and the ionization rate, the plasmas
frequency variation, and the polarization of atoms (ions) is analysed. The numerical
results indicate that, at high frequency, the polarization of atoms (ions) plays a
more important role than plasma frequency variation in modulating the laser
frequency, and the laser frequency variation is different at different positions of
the laser pulse. 相似文献
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LI Xiao-Gang 《理论物理通讯》2012,57(6):1053-1058
Above-threshold ionizations of rare gas atoms excited by polarized femtosecond laser pulses are investigated. The photoelectron momentum spectra are obtained applying the strong-field approximation (SFA) theory. It is found that, distribution of the emitted photoelectrons varies with different polarizations of laser pulses. We have interpreted the relationship between the observed distribution and the laser polarization taking advantage of tunneling ionization theory and simple-man model. The polarization sensitivity indicates that one can easily manipulate the photoelectron distribution by controlling the polarization of the exciting pulse. 相似文献
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Kelkensberg F Siu W Pérez-Torres JF Morales F Gademann G Rouzée A Johnsson P Lucchini M Calegari F Sanz-Vicario JL Martín F Vrakking MJ 《Physical review letters》2011,107(4):043002
We report experiments where hydrogen molecules were dissociatively ionized by an attosecond pulse train in the presence of a near-infrared field. Fragment ion yields from distinguishable ionization channels oscillate with a period that is half the optical cycle of the IR field. For molecules aligned parallel to the laser polarization axis, the oscillations are reproduced in two-electron quantum simulations, and can be explained in terms of an interference between ionization pathways that involve different harmonic orders and a laser-induced coupling between the 1sσ(g) and 2pσ(u) states of the molecular ion. This leads to a situation where the ionization probability is sensitive to the instantaneous polarization of the molecule by the IR electric field and demonstrates that we have probed the IR-induced electron dynamics with attosecond pulses. 相似文献
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Rudenko A de Jesus VL Ergler T Zrost K Feuerstein B Schröter CD Moshammer R Ullrich J 《Physical review letters》2007,99(26):263003
We report on a kinematically complete experiment on nonsequential double ionization of He by 25 fs 800 nm laser pulses at 1.5 PW/cm;{2}. The suppression of the recollision-induced excitation at this high intensity allows us to address in a clean way direct (e,2e) ionization by the recolliding electron. In contrast with earlier experimental results, but in agreement with various theoretical predictions, the two-electron momentum distributions along the laser polarization axis exhibit a pronounced V-shaped structure, which can be explained by the role of Coulomb repulsion and typical (e,2e) kinematics. 相似文献
15.
The effect of electron initial longitudinal velocity on the non-sequential double ionization process in an elliptically polarized laser field
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The effect of initial longitudinal velocity of the tunnelled electron on the non-sequential double ionization(NSDI) process in an elliptically polarized laser field is studied by a semiclassical model.We find that the non-zero initial longitudinal velocity has a suppressing effect on single-return collision(SRC) events in the double ionization process,more specifically,it results in an obvious reduction in the center part of the correlation momentum distributions in the direction of the major polarization axis(z axis) and makes the distribution of single-return collision in the minor polarization axis(x axis) become narrower. 相似文献
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铀原子多色三光子共振电离谱研究 总被引:2,自引:1,他引:1
利用Nd:YAG二倍频激光同步泵浦的脉冲染料激光系统、原子束装置、飞行时间质谱和Boxcar技术测量了^238U的多色三光子共振电离谱。研究了电场对铀原子第一激发态的影响。解决了如何确定三角三光子共振电离谱图中所含的单色,双色和三色共振电离峰的问题。 相似文献
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Alnaser AS Osipov T Benis EP Wech A Shan B Cocke CL Tong XM Lin CD 《Physical review letters》2003,91(16):163002
We have measured momentum spectra and branching ratios of charged ionic fragments emitted in the double ionization of D2 (and H2) molecules by short intense laser pulses. We find high-energy coincident D+ (and H+) ion pairs with kinetic energy releases between 8 and 19 eV which appear for linearly polarized light but are absent for circularly polarized light. The dependence on the polarization, the energy distributions of the ions, and the dependence on laser intensity of yield ratios lead us to interpret these ion pairs as due to a rescattering mechanism for the double ionization. A quantitative model is presented which accounts for the major features of the data. 相似文献
18.
The effect of electron initial longitudinal velocity on non-sequential double ionization process in elliptically polarized laser field
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The effect of initial longitudinal velocity of the tunnelled electron on the non-sequential double ionization (NSDI) process in elliptically polarized laser field is studied by a semiclassical model. We find that the non-zero initial longitudinal velocity has a suppressing effect on single-return collision (SRC) events in double ionization process, more specifically, it results in an obvious reduction in the center part of the correlation momentum distributions in the direction of the major polarization axis (z axis) and makes the distribution of single-return collision in the minor polarization axis (x axis) become narrow. 相似文献
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I. A. Kotelnikov A. V. Borodin A. P. Shkurinov 《Journal of Experimental and Theoretical Physics》2011,112(6):946-951
The probability of multiphoton ionization of atoms in a laser radiation field containing an additional second harmonic is
calculated by the imaginary time method [9, 10]. The conditions are found when the second-harmonic contribution to the ionization
of atoms dominates over that of the first harmonic. It is shown that the average momentum of photoelectrons ejected from atoms
depends on the phase shift between the first and second harmonics and their mutual polarization. The obtained asymptotic expressions
can be used for the qualitative explanation of experiments on generation of terahertz radiation from the optical breakdown
region in gas in the focus of a femtosecond laser. 相似文献
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Zeidler D Staudte A Bardon AB Villeneuve DM Dörner R Corkum PB 《Physical review letters》2005,95(20):203003
We investigate the dynamics of double ionization in aligned nitrogen molecules. An ultrashort, weak laser pulse creates an aligned ensemble of molecules that is ionized with a subsequent, strong probe pulse. We find that the two electrons involved in nonsequential double ionization more likely exit the molecule in the same direction if it is parallel to the probe laser polarization, indicating that they are ejected within a few hundred attoseconds of each other. Double ionization is less probable and takes longer for perpendicular molecules. 相似文献