Theoretical study of the influence of intense femtosecond laser field on the evolution of the wave packet and the population of NaRb molecule

Employing the two-state model and the time-dependent wave packet method, we have investigated the influences of the parameters of the intense femtosecond laser field on the evolution of the wave packet, as well as the population of ground and double-minimum electronic states of the NaRb molecule. For the different laser wavelengths, the evolution of the wave packet of 6{ }^1／Sigma ^ ＋ state with time and internuclear distance is different, and the different laser intensity brings different influences on the population of the electronic states of the NaRb molecule. One can control the evolutions of wave packet and the population in each state by varying the laser parameters appropriately, which will be a benefit for the light manipulation of atomic and molecular processes.

Influence of laser fields on the vibrational population of molecules and its wave-packet dynamical investigation

The time-dependent wave packet method is used to investigate the influence of laser-fields on the vibrational population of molecules. For a two-state system in laser fields, the populations on different vibrational levels of the upper and lower electronic states are given by wavefunctions obtained by solving the Schrbdinger equation with the split- operator method. The calculation shows that the field parameters, such as intensity, wavelength, duration, and delay time etc. can have different influences on the vibrational population. By varying the laser parameters appropriately one can control the evolution of wave packet and so the vibrational population in each state, which will benefit the light manipulation of atomic and molecular processes.

Time-dependent approach to the double-channel dissociation of the NaCs molecule induced by pulsed lasers

The dynamics of the double-channel dissociation of the NaCs molecule is investigated by using the time-dependent wave packet （TDWP） method with the ＂split operator-Fourier transform＂ scheme. At a given wavelength and intensity of laser pulse, the population of each state changing with time is obtained. The photo-absorption spectra and kinetic- energy distribution of the dissociation fragments, which exhibit vibration-level structure and dispersion of the wave packet, respectively, are also obtained. The results show that by increasing the laser intensity, one can find not only the band center shift of the photo-absorption spectrum, but also the change of the fragment energy. The appearance of the diffusive band in the photo-absorption spectrum and the multiple peaks in the kinetic-energy spectrum can be attributed to the effects of the predissoeiation limit and the external field.

Quantum dynamics of dissociative adsorption of H_2 and D_2:The time-dependent wave packet method

A time dependent quantum wave packet method was used to study the dynamics of dissociative adsorption of H 2 and D 2 on a flat and static surface. The molecule surface interaction is described using a modified London Eyring Polanyi Sato (LEPS) type potential for the H 2/Ni(100) system. The three dimensional (3 D) dissociation probabilities were calculated for different initial rovibrational states as a function of initial incident energies. Our results show that the dissociation of the diatomic rotational states whose quantum numbers satisfy j+m =odd is forbidden at low energies for the homonuclear H 2 and D 2 due to the selection rule. The effect of the rotational orientation of diatoms on adsorption predicts that the in plane rotation (m=j) is more favorable for dissociation than the out of plane rotation (m=0) . Enhanced dissociation for vibrationally excited molecules and the significant enhancement of the dissociation probability of H 2 when compared to D 2 were explained reasonably in terms of quantum mechanical zero point energies, the tunneling effect and the reflection from an activation barrier.

Quantum Dynamics Study on D＋OD＋ Reaction： Competition between Exchange and Abstraction Channels

Quantum dynamics for the D＋OD＋ reaction at the collision energy range of 0.0-1.0 eV was studied on an accurate ab initio potential energy surface. Both of the endothermic abstraction （D＋OD＋-→O＋＋D2） and thermoneutral exchange （D＋OD＋--＊D＋OD＋） channels were investigated from the same set of time-dependent quantum wave packets method under cen- trifugal sudden approximation. The reaction probability dependence with collision energy, the integral cross sections, and the thermal rate constant of the both channels are calculated. It is found that there is a convex structure in the reaction path of the exchange reaction. The calculated time evolution of the wave packet distribution at J=0 clearly indicates that the convex structure significantly influences the dynamics of the exchange and abstraction channels of title reaction.

Reaction mechanism of D + ND→N + D_2 and its state-to-state quantum dynamics

The quantum state-to-state calculations of the D + ND→N + D_2 reaction are performed on a potential energy surface of 4 A'' state. The state-resolved integral and differential cross sections and product state distributions are calculated and discussed. It is found that the rotational distribution, rather than the vibrational distribution, of the product has an obvious inversion. Due to the fact that it is a small-impact-parameter collision, its product D_2 is mainly dominated by rebound mechanism, which can lead to backward scattering at low collision energy. As the collision energy increases, the forward scattering and sideward scattering begin to appear. In addition, the backward collision is also found to happen at high collision energy, through which we can know that both the rebound mechanism and stripping mechanism exist at high collision energy.

Non-adiabatic quantum dynamical studies of Na(3p) + HD(v = 1, j5) = 0)→NaH/NaD + D/H reaction

Non-adiabatic dynamical calculations are carried out for the Na(3 p)+HD(ν = 1, j = 0)→NaH/NaD+D/H reaction on the diabatic potential energy surfaces of Wang et al.(Sci. Rep. 2018, 8, 17960) by using the time-dependent wave packet method. The state-to-state integral cross sections and differential cross sections of two reaction channels(NaH/NaD+D/H)are calculated for collision energy up to 0.4 eV. The cross section branching ratio indicates that the dominant reaction channel changes from NaD+H to NaH+D when the collision energy is larger than 0.227 eV. The products from two reaction channels both prefer to form in vibrationally cold but rotationally hot states, and they both tend to forward scattering.

Time-dependent wave packet approach to the pulse delay effect upon RbI photoelectron spectrum

The time-resolved photoelectron spectrum (TRPES) of Rbl molecule is simulatedusing the time-dependent wave-packet method. Both the normal three-photon ionization process andauto-ionization process are involved in the simulation. The calculated results show that the changeof delay time will influence the shape of the photoelectron spectrum (PES), and the influence issubstantially due to the existence of the crossing between excited states and the strong laser fieldwhich will change the position of relevant curves.

State-to-state quantum dynamics of the N(~4S)+H_2(X^1Σ^+) → NH(X^3Σ^-)+H(~2S) reaction and its reaction mechanism analysis

Quantum state-to-state dynamics of the N(4S) + H-2(X1+Σ) → NH(X3Σ) + H(2S) reaction is reported in an accurate novel potential energy surface constructed by Zhai et al.(2011 J. Chem. Phys. 135 104314). The time-dependent wave packet method, which is implemented on graphics processing units, is used to calculate the differential cross sections. The influences of the collision energy on the product state-resolved integral cross sections and total differential cross sections are calculated and discussed. It is found that the products NH are predominated by the backward scattering due to the small impact parameter collisions, with only minor components being forward and sideways scattered, and have an inverted rotational distribution and no inversion in vibrational distributions; both rebound and stripping mechanisms exist in the case of high collision energies.

HD^+分子的强场光解离动力学及其量子调控的理论研究

利用精确求解原子核与电子耦合运动的三维含时量子波包法,理论研究了HD+分子在强激光场中的光解离动力学,并给出了量子调控HD+分子光解离通道的理论方案.通过分析HD+分子在不同的初始振动态和激光场强度下的光解离动力学过程及其解离核动能谱,得出了HD+分子的光解离机理及其随激光场强度的变化规律.研究结果表明,利用激光场的强度可以实现HD+分子光解离通道的量子调控.当激光场强度I1=4.0×1013 W/cm2时,HD+分子的光解离主要是通过净单光子吸收解离和净双光子吸收解离;当激光场强度增大到I2=2.0×1014 W/cm2时,直接双光子吸收解离取代了净单光子吸收解离,净双光子吸收解离的比重也下降了.

飞秒泵浦-探测脉冲下布居转移的场依赖研究（英文）

利用含时波包法研究并首次量化了强飞秒泵浦-探测激光场中泵浦场强、泵浦波长和脉宽对三态梯型K_2分子态布居数的影响。泵浦场强、泵浦波长和脉宽影响Rabi振荡,导致电子态布居数的周期性变化。量化场参数对激发态布居数的影响表明变化频率随着泵浦场强和脉宽的增大而变化。结果为实验上实现分子的光控制和进一步研究K_2分子的动力学性质提供了重要参考。

Control of reaction channels of CsI molecule by ultra-short laser pulse

The influence of the ultra-short pulse wavelength on the populations in the three electronic states of CsI molecule is investigated using the time-dependent wave packet method. The calculated results show that the populations in the two excited states approach to the maxima at the wavelengths of 369 nm and 297 nm, respectively. The photodissociation reaction channels of the CsI molecule can be chosen by controlling the pump pulse wavelength.

D_2在Ni(100)表面离解吸附的量子动力学研究

用量子含时波包法研究了Ｄ２在镍表面顶－桥位上离解吸附量子动力学．计算了不同入射动能及初始振转态的离解几率．讨论了分子的同核对称性、转动取向和振动激发对离解几率的影响，并与其他理论计算结果做了比较．

Manifestation of external field effect in time-resolved photo-dissociation dynamics of LiF

The photo-dissociation dynamics of LiF is investigated with newly constructed accurate ab initio potential energy curves （PECs） using the time-dependent quantum wave packet method. The oscillations and decay of the wave packet on the adiabats as a function of time are given, which can be compared with the femtosecond transition-state （FTS） spectroscopy. The photo-absorption spectra and the kinetic-energy distribution of the dissociation fragments, which can exhibit the vibration-level structure and the dispersion of the wave packet, respectively, are also obtained. The investigation shows a blue shift of the band center for the photo-absorption spectrum and multiple peaks in the kinetic-energy spectrum with increasing laser intensity, which can be attributed to external field effects. By analyzing the oscillations of the wave packet evolving on the upper adiabat, an approximate inversion scheme is devised to roughly deduce its shape.

The effect of field modulation on the vibrational population of the photoassociated NaK and its dynamics

This paper presents calculation results for the photoassociation of a NaK molecule with a two-color modulated laser and gives a detailed analysis about them.For the two-step photoassociation process in intense fields,the effect of two-color modulated laser parameters,such as relative phase,envelope period,and laser intensity,on the population of the molecular electronic state can be obtained by solving the time-dependent Schrodinger equation through the quantum wave packet method.The numerical simulation shows not only that the influence of laser parameters on the vibrational distribution presents some regularity,but also that a higher population in the ground electronic state can be realized through adjusting these laser parameters.

Theoretical simulation of the photoassociation process for NaCs

We investigate the two-step association process of NaCs using the time-dependent wave packet method.Ground state atoms can be photoassociated to the low vibrational levels of the ground state for an NaCs molecule by the two-step association.The time-dependent Schro¨dinger equation of the association process is solved within a three-state model and the wave packet is propagated with the ＂split operator-Fourier transform＂ scheme and the rotating-wave approximation（RWA）.The vibrational population distribution of the ground state can be obtained by projecting the wave packet to every vibrational level of the ground state.The results not only show that for NaCs achievement of photoassociation production is accompanied by the photodissociation of the higher vibrational molecules,but also show that the vibrational distribution in lower vibrational levels of the ground state changes with the laser parameters.

Non-adiabatic Couplings Induced Complex-Forming Mechanism in H+MgH^(+)→Mg^(+)+H_(2) Reaction

A chemical process may involve multiple adiabatic electronic states, and non-adiabatic couplings play an important role in the reaction mechanism. In this work, the effect of non-adiabatic couplings in the H+MgH;→Mg;+H;reaction are studied using the time-dependent wave packet method and trajectory surface hopping method. The calculated results show that the reaction follows a direct abstraction process when the non-adiabatic couplings are neglected. However, when non-adiabatic couplings are included in the calculations, a longlived excited state complex(MgH_(2)+)*can be formed during the reaction. These direct and complex-forming reaction pathways are revealed by trajectory surface hopping calculations.The non-adiabatic couplings induced complex-forming mechanism not only increases the reactivity but also has significant effect on the product vibrational state distribution.

State-to-state dynamics of F(~2P) + HO(~2Π) → O(~3P) + HF(~1Σ^+)reaction on 1~3A〞 potential energy surface

State-to-state time-dependent quantum dynamics calculations are carried out to study F（2P） ＋ HO（2ЦП（→ O（3P） ＋ HF（1∑＋） reaction on 1^3A″ ground potential energy surface （PES）. The vibrationally resolved reaction probabilities and the total integral cross section agree well with the previous results. Due to the heavy-light-heavy （HLH） system and the large exoergicity, the obvious vibrational inversion is found in a state-resolved integral cross section. The total differential cross section is found to be forward-backward scattering biased with strong oscillations at energy lower than a threshold of 0.10 eV, which is the indication of the indirect complex-forming mechanism. When the collision energy increases to greater than 0.10 eV, the angular distribution of the product becomes a strong forward scattering, and almost all the products are distributed at θt = 0°. This forward-peaked distribution can be attributed to the larger J partial waves and the property of the F atom itself, which make this reaction a direct abstraction process. The state-resolved differential cross sections are basically forward-backward symmetric for v′ = 0, 1, and 2 at a collision energy of 0.07 eV; for a collision energy of 0.30 eV, it changes from backward/sideward scattering to forward peaked as v′ increasing from 0 to 3. These results indicate that the contribution of differential cross sections with more highly vibrational excited states to the total differential cross sections is principal, which further verifies the vibrational inversion in the products.

Quantum dynamics studies on the non-adiabatic effects of H+LiD reaction

After the Big Bang,chemical reactions of hydrogen with LiH and its isotopic variants played an important role in the late stage of recombination.Moreover,these reactions have attracted the attention of experts in the field of molecular dynamics because of its simple structure.Electronically non-adiabatic effects play a key role in many chemical reactions,while the related studies in LiH2 reactive system and its isotopic variants are not enough,so the microscopic mechanism of this system has not been fully explored.In this work,the microscopic mechanism of H+LiD reaction are performed by comparing both the adiabatic and non-adiabatic results to study the non-adiabatic effects.The reactivity of R1(H+LiD→Li+HD)channel is inhibited,while that of R2(H+LiD→D+LiH)channel is enhanced when the non-adiabatic couplings are considered.For R1 channel,a direct stripping process dominates this channel and the main reaction mechanism is not influenced by the non-adiabatic effects.For R2 channel,at relatively low collision energy,the dominance changes from a rebound process to the complex-forming mechanism when the non-adiabatic effects are considered,whereas the rebound collision approach still dominates the reaction at relatively high collision energy in both calculations.The presented results provide a basis for further detailed study on this importantly astrophysical reaction system.

基于GPU的量子含时波包方法模拟星际化学反应

本文将探讨利用GPU加速的量子含时波包方法求解薛定谔方程精确的预测星际中的基元化学反应的各种信息。文章首先介绍了基于GPU的量子含时波包方法,其次探讨了用该方法去模拟型星际中的Li与H2^+以及C^++H2反应的过程及意义,最后阐述了在该方法在量子力学与GPU编程课程中学习中也具有一定意义。