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1.
通过求解D2分子在飞秒激光场中的含时薛定谔方程,研究了室温下D2分子在超快飞秒激光驱动下的的转动波包动力学. 选择用第一束超短飞秒脉冲与温度为300 K的D2分子系综相互作用产生一个相干转动波包,用第二束超短飞秒脉冲在波包的1/4和3/4恢复周期选择操纵D2分子取向. 研究结果表明,通过选择两束超短飞秒脉冲的延迟时间,可以有效控制D2分子转动波包中奇偶态的相对布居,从而选择性的控制D2分子取向. 相似文献
2.
Selective excitation of the molecular rotational wave packet by two time-delayed laser pulses
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In this paper, we investigate the control of the molecular wave packet of a linear molecule by two femtosecond laser pulses. It is shown that the odd and the even rotational wave packets created by a single laser pulse can be selectively excited by accurately controlling the time delay of another laser pulse. By inserting the peak of the second laser pulse at the position of maximum or minimum value around quarter or three quarter rotational period of the slope curve with odd (or even) rotational wave packet contribution that is created by the first laser pulse, the odd rotational wave packet can be enhanced (or suppressed) while the even rotational wave packet is suppressed (or enhanced). As a result, the molecular alignments around quarter and three quarter rotational periods can be obtained. Moreover, it is also shown that by inserting the second laser pulse around the quarter or three quarter rotational periods, the changes in the maximum degree of the molecular alignment for the odd and the even rotational wave packet contributions are consistent with their corresponding slope curves at these positions. 相似文献
3.
Ortigoso J 《Physical review letters》2004,93(7):073001
The existence of states for which molecular alignment can be maintained for long periods of time is shown. These states, consisting of coherent superpositions of rotational states, are found among cyclic states of the generalized Floquet operator corresponding to a molecule in a short nonresonant laser pulse. For a single pulse alignment can be maintained, in some cases, for more than 40 times the pulse duration. Because of the special properties of these coherent states, arbitrarily long alignment can be achieved by using well-timed pulse trains. 相似文献
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5.
《中国光学快报(英文版)》2018,(10)
In this Letter, we study the molecular alignment and orientation driven by two elliptically polarized laser pulses.It is shown that the field-free molecular alignment can be achieved in a three-dimensional(3D) case, while the field-free molecular orientation is only along the x and y directions, and that the field-free alignment and orientation along different axes are related to the populations of the rotational states. It is demonstrated that changing the elliptic parameter is efficient for controlling both in-pulse and post-pulse molecular alignment and orientation. The delay time also has an influence on the field-free molecular alignment and orientation. 相似文献
6.
Bisgaard CZ Poulsen MD Péronne E Viftrup SS Stapelfeldt H 《Physical review letters》2004,92(17):173004
We show experimentally that field-free alignment of iodobenzene molecules, induced by a single, intense, linearly polarized 1.4-ps-long laser pulse, can be strongly enhanced by dividing the pulse into two optimally synchronized pulses of the same duration. For a given total energy of the two-pulse sequence the degree of alignment is maximized with an intensity ratio of 1:3 and by sending the second pulse near the time where the alignment created by the first pulse peaks. 相似文献
7.
We show that the filamentation dynamics of a femtosecond laser probe pulse can be readily controlled by properly matching it to the quantum revivals of pre-aligned molecules prepared through impulsive rotational Raman excitation with an advancing ultrashort pump pulse. Several features of the filamentation process including supercontinuum generation, the length of the plasma channel generated in the wake of the filament, the associated secondary radiations and the multiple filamentation pattern are all easily modified by tuning the cross phase modulation induced by the field-free revivals of molecular alignment, through the delay between the pump and the probe pulses. We show that molecular alignment can also be used to generate conical waves with extremely short intensity spike called shocked X-waves and to further tune the frequency of a few-cycle laser pulse in the wake of a self-guided intense filament. 相似文献
8.
The dynamic alignment and post-ionization alignment of nitrogen molecules are investigated while considering the effect of tunneling ionization. The effects of tunneling ionization on the angular distribution are calculated when the molecules are irradiated by different laser intensities. The results show that laser intensity directly affects the time and extent of dynamic alignment. Furthermore, the extent of post-ionization alignment is not only determined by laser intensity but also affected by the final extent of dynamic alignment. The post-ionization alignment will dominate during the process of molecular (or molecular ion) rotational alignment for femtosecond laser pulse. The time of tunneling ionization is a significant factor to the final ensemble angular distribution of molecular ions when laser intensity is low. 相似文献
9.
《中国光学快报(英文版)》2018,(12)
We report on an experimental investigation on the dynamic decoherence process of molecular rotational wavepackets during femtosecond laser filamentation based on time-dependent mean wavelength shifts of a weak probe pulse. Details of periodic revival structures of transient alignment can be readily obtained from the measured shifted spectra due to the periodic modulation of the molecular refractive index. Using the method, we measured decoherence lifetimes of molecular rotational wavepackets in N_2 and O_2 under different experimental conditions. Our results indicate that decoherence lifetimes of molecular rotational wavepackets are primarily determined by the relative population of rotational states in the wave packet and intermolecular collisions,rather than the focusing intensity. 相似文献
10.
Guiping Zeng Fengjiao Zhong Chengyin Wu Hongbing Jiang Qihuang Gong 《Laser Physics》2009,19(8):1691-1696
Field-free molecular alignment can be achieved by nonadiabatic rotational excitation of molecules with strong femtosecond laser pulses. We experimentally and theoretically demonstrate that the degree of alignment can be improved with multi-pulse excitation. An approach is proposed to tune the frequency of few-cycle pulses using field-free alignment of molecules. 相似文献
11.
Angular distributions of CH3I fragment ions under the irradiation of single pulse and trains of ultrashort laser pulses
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The angular distribution of CH3I is investigated experimentally using a single Fourier transform-limited laser pulse and a pulse train, where a 90-fs 800-nm linearly polarized laser field with a moderate intensity of 2.8×1013 W/cm2 is used. The dynamic alignment is demonstrated in a single pulse experiment. Moreover, a pulse train is used to optimize the molecular alignment, and the alignment degree is almost identical to that with the single pulse. The results are analysed by using chirped femtosecond laser pulses, and it demonstrates that the structure of pulse train rather than its effective duration is crucial to the molecular alignment. 相似文献
12.
结合飞秒激光在研究分子激发态弛豫动力学中的应用,介绍了几种飞秒时间分辨实验中确定泵浦激光脉冲与探测激光脉冲的相关函数和时间零点的方法.对于波长在可见波段的泵浦和探测激光脉冲,我们可以利用非线性光学的技术手段,探测泵浦光与探测光的和频光的强度随二者间的时间延迟的变化来确定相关函数和时间零点;对于波长在紫外甚至更短的波段的泵浦和探测激光脉冲,由于单脉冲能量比较低,目前还很难利用技术手段来测定泵浦激光与探测激光的相关函数及时间零点,可以利用某些原子气体(如Xe)或某些具有短寿命态的分子作平行实验进行间接测量. 相似文献
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14.
A theory of classical rotation and alignment of diatomic molecules with and without permanent dipole moments and of their
molecular ions in strong laser fields is developed. The actions of both cw and pulsed laser fields is considered. Conditions
under which molecular axes are aligned with the field, which is presumed to be linearly polarized, have been determined. The
analysis leads to a conclusion that molecules exposed to ultrashort laser pulses continue to rotate even after the end of
the laser pulse. The effect of dynamical chaos on the rotational angular velocity in strong laser field is discussed.
Zh. éksp. Teor. Fiz. 113, 573–582 (February 1998) 相似文献
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16.
A.S. Akhmanov V.Yu. Baranov V.D. Pismenny V.N. Bagratashvili Yu.R. Kolomiisky V.S. Letokhov E.A. Ryabov 《Optics Communications》1977,23(3):357-361
The investigation of the role of pulse duration in the absorption of CO2 laser pulses by polyatomic molecules has shown that the rotational relaxation does not contribute significantly to the absorption of intense IR radiation. This proves the existence of purely radiative depletion of all rotational states in monochromatic fields of moderate intensity. 相似文献
17.
Daniel Weidinger 《Molecular physics》2013,111(13-14):1999-2008
Accurate rotation–vibration energy levels and transition dipoles of the molecule thiophosgene are used to model the execution of quantum gates with shaped laser pulses. Qubits are encoded in 2 n vibrational computing states on the ground electronic surface of the molecule. Computations are carried out by cycling amplitude between these computing states and a gateway state with a shaped laser pulse. The shaped pulse that performs the computation is represented by a physical model of a 128–1024 channel pulse shaper. Pulse shapes are optimized with a standard genetic algorithm, yielding experimentally realizable computing pulses. The robustness of optimization is studied as a function of the vibrational states selected, rotational level structure, additional vibrational levels not assigned to the computation, and compensation for laser power variation across a molecular ensemble. 相似文献
18.
N.E. Karatzas 《Optics Communications》2006,267(2):498-504
Calculations are presented for the first four (odd and even) harmonics of an 800 nm laser from a gold surface, with pulse widths ranging from 100 down to 14 fs. For peak laser intensities above 1 GW/cm2 the harmonics are enhanced because of a partial depletion of the initial electron states. At 1011 W/cm2 of peak laser intensity the calculated conversion efficiency for 2nd-harmonic generation is 3 × 10−9, while for the 5th-harmonic it is 10−10. The generated harmonic pulses are broadened and delayed relative to the laser pulse because of the finite relaxation times of the excited electronic states. The finite electron relaxation times cause also the broadening of the autocorrelations of the laser pulses obtained from surface harmonic generation by two time-delayed identical pulses. Comparison with recent experimental results shows that the response time of an autocorrelator using nonlinear optical processes in a gold surface is shorter than the electron relaxation times. This seems to indicate that for laser pulses shorter than ∼30 fs, the fast nonresonant channel for multiphoton excitation via continuum-continuum transitions in metals becomes important as the resonant channel becomes slow (relative to the laser pulse) and less efficient. 相似文献
19.
Field-free molecular orientation induced by combined femtosecond single- and dual-color laser pulses:The role of delay time and quantum interference
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The coherent control of field-free molecular orientation of CO with combined femtosecond single- and dual-color laser pulses has been theoretically studied. The effect of the delay time between the femtosecond single- and dual-color laser pulses is discussed, and the physical mechanism of the enhancement of molecular orientation with pre-alignment of the molecule is investigated. It is found that the basic mechanism is based on the creation of a rotational wave packet by the femtosecond single-color laser pulse. Furthermore, we investigate the interference between multiple rotational excitation pathways following pre-alignment with femtosecond single-color laser pulse. It is shown that such interference can lead to an enhancement of the orientation of CO molecule by a factor of 1.6. 相似文献
20.
We investigate strategies for field-free three dimensional molecular axis alignment using strong nonresonant laser fields under experimentally realistic conditions. Using the polarizabilites and rotational constants of an asymmetric top rotor molecule (ethene, C2H4), we consider three different methods for axis alignment of a Boltzmann distribution of rotors at 4 K. Specifically, we compare the use of impulsive kick laser pulses having both linear and elliptical polarization to the use of elliptically polarized switched laser pulses. We show that an enhanced degree of field-free three dimensional alignment of ground vibronic state molecules obtains from the use of two orthogonally polarized, time-separated laser pulses. 相似文献