共查询到19条相似文献,搜索用时 140 毫秒
1.
采用飞秒时间分辨质谱技术结合飞秒时间分辨光电子影像技术研究了苯乙炔分子电子激发态超快非绝热弛豫动力学.用235 nm光作为泵浦光,将苯乙炔分子激发到第二激发态S2,用400 nm光探测激发态的演化过程.时间分辨的母体离子的变化曲线用指数和高斯函数卷积得到不同的两个组分,一个是超快衰减组分,时间常数为116 fs,一个是慢速组分,时间常数为106 ps.通过分析时间分辨的光电子影像得到光电子动能分布,结合时间分辨光电子能谱数据发现,时间常数为116 fs的快速组分反映了S2态向S1态的内转换过程.实验还表明S1态通过内转换被布局后向T1态的系间窜跃过程为重要的衰减通道.本工作为苯乙炔分子S2态非绝热弛豫动力学提供了较清晰的物理图像. 相似文献
2.
《物理学报》2020,(10)
飞秒时间分辨光电子影像技术和飞秒时间分辨质谱技术相结合,研究了2-甲基吡嗪分子电子激发态超快非绝热弛豫动力学.用323 nm光作为泵浦光,把2-甲基吡嗪分子激发到第一激发态S_1,用400 nm光探测激发态演化过程.通过时间分辨质谱技术测得S_1态的寿命为98 ps.实验中,实时观察到了单重态S_1向三重态T_1的系间交叉过程.通过分析发现,跟吡嗪分子S_1态的动力学过程不同,2-甲基吡嗪分子激发到S_1态后,不仅S_1→T_1系间交叉过程是S_1态主要衰减通道,S_1→S_0内转换过程也是S_1态另一个主要衰减通道.发挥飞秒时间分辨光电子影像技术的优点,实验上得到不同泵浦-探测时间延迟的光电子角分布,从角分布信息结合光电子能谱信息,尝试观察2-甲基吡嗪分子的非绝热无场准直,但由于2-甲基吡嗪分子对称性比吡嗪分子更低,对称性更低分子准直现象的观察更有挑战性,在实验中未能观察到非绝热准直动力学.本工作为2-甲基吡嗪分子S_1态非绝热弛豫动力学提供了较清楚的物理图像. 相似文献
3.
4.
利用时间分辨的飞秒光电子影像技术结合时间分辨的质谱技术,研究了2,6-二甲基吡啶分子锥形交叉超快动力学过程. 2,6-二甲基吡啶分子吸收266 nm泵浦光从基态跃迁至S2态(π-π*). 母体离子时间变化曲线包含两个指数函数,一个是时间常数为635 fs的快速组分,另一个是时间常数为4.37 ps的慢速组分. 通过时间分辨光电子影像得到的时间依赖的光电子角度分布和能量分辨的光电子谱分布提供了S2态演变的动力学信息. 简言之,快速组分反映了通 相似文献
5.
《物理学报》2020,(7)
拓扑半金属磷化钼(MoP)同时具有三重和二重简并费米子.为了研究其费米面以上的激发态超快动力学特性,对其进行了时间分辨超快泵浦-探测实验.获得了MoP的准粒子动力学,包含来源于电子-声子散射的快分量,寿命为0.3 ps,以及来源于声子-声子散射的慢分量,寿命为150 ps.温度依赖的研究表明,快分量和慢分量的弛豫寿命均随着温度的增加产生微小增大.同时还激发并探测到一支相干态声学支声子,其由热应力引起,频率为0.033 THz且不随温度而改变.对于MoP激发态准粒子超快动力学以及相干态声子的研究为理解该体系总体的激发态超快动力学特性以及电子-声子相互作用对温度的依赖提供了有益的实验依据. 相似文献
6.
飞秒激光技术的出现使得实时探测与跟踪激发态超快弛豫动力学过程成为可能,并能够给出激发态动力学过程清晰的物理图像。而在飞秒时间分辨实验中,泵浦-探测相关函数和时间零点直接影响实验结果的可靠性和准确性。本文结合飞秒激光在分子激发态超快动力学过程中的应用进展,介绍了根据实验条件和要求,在具体实验过程中泵浦-探测相关函数测量和时间零点确定的几种方法。实验中选择可见光作为泵浦光和探测光时,可以通过测定随泵浦-探测时间延迟变化的泵浦激光与探测激光的和频/差频光强来确定泵浦探测交叉相关函数和时间零点;而选择中心波长在紫外甚至真空紫外的激光脉冲作为泵浦光或探测光时,泵浦-探测交叉相关函数通常采用校正的方法测量。 相似文献
7.
本文利用飞秒激光泵浦-探测质谱和离子成像研究了NO_2分子的超快解离动力学.结果表明NO~+离子的动能释放包含两个部分,分别对应的能量是0.05和0.25 eV,并且指认了它们叫能的解离通道.NO~+离子通道分辨的瞬态测量提供了区分超快解离路径贡献的方法,不同动能释放的离子信号变化曲线可以通过双e指数函数进行拟合.其中衰减时间为0.25 ps的快速变化部分产生于里德堡态的演化.变化较慢的信号部分是山两个竞争的通道产生的,其中一个通道是吸收一个400 nm光子到A~2B_2激发态,它的衰减寿命是30 ps;另一个慢的通道是吸收三个400 nm光子到一个价电子类型的里德堡态,它的衰减寿命是短于7.2 ps.通道和时间分辨的实验测量对于区分分子复杂的超快解离动力学具有非常大的潜力. 相似文献
8.
《化学物理学报》2019,(3)
本文利用飞秒激光泵浦-探测质谱和离子成像研究了NO_2分子的超快解离动力学.结果表明NO~+离子的动能释放包含两个部分,分别对应的能量是0.05和0.25 eV,并且指认了它们叫能的解离通道.NO~+离子通道分辨的瞬态测量提供了区分超快解离路径贡献的方法,不同动能释放的离子信号变化曲线可以通过双e指数函数进行拟合.其中衰减时间为0.25 ps的快速变化部分产生于里德堡态的演化.变化较慢的信号部分是山两个竞争的通道产生的,其中一个通道是吸收一个400 nm光子到A~2B_2激发态,它的衰减寿命是30 ps;另一个慢的通道是吸收三个400 nm光子到一个价电子类型的里德堡态,它的衰减寿命是短于7.2 ps.通道和时间分辨的实验测量对于区分分子复杂的超快解离动力学具有非常大的潜力. 相似文献
9.
10.
11.
时间分辨光电离是揭示多原子分子激发态动力学的一种强有力的实验方法.根据收集信号的种类,可以采用不同的测量方法:时间分辨离子产率谱(TR-IYS)和时间分辨光电子成像(TR-PEI).本文综述介绍了光电离测量与电子结构的基本概念,以及在实验上区分不同几何结构之间的振荡波包运动的几个重要研究工作,并举例说明飞秒TR-IYS和TR-PEI是如何被用来探测激发态势能面上相干振动波包的演化过程. 相似文献
12.
T. Mančal V. May 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,18(4):633-643
Non-Markovian dynamics in open quantum systems is characterized by a time-non-locality in the equation of motion valid for
the reduced density operator. An expansion of this density matrix equation with respect to Laguerre polynomials is used to
tackle the time-non-locality. The applicability and the numerical limitations of the method are discussed in detail. In order
to illuminate the characteristics of non-Markovian dynamics the reference example is studied of a single quantum degree of
freedom moving in a harmonic potential and being embedded in a heat bath. If interpreted as the photoinduced dynamics of nuclear
motion in polyatomic molecules we can suggest two clear signatures of non-Markovian dynamics observable in ultrafast optical
experiments, firstly a pronounced and somewhat irregular oscillatory behavior of the vibrational level populations, and secondly
a separation of the vibrational wavepacket into a double-structure.
Received 12 April 2000 and Received in final form 2 September 2000 相似文献
13.
Toshinori SUZUKI 《Proceedings of the Japan Academy. Series B, Physical and biological sciences》2013,89(1):1-15
Polyatomic molecules have several electronic states that have similar energies. Consequently, their chemical dynamics often involve nonadiabatic transitions between multiple potential energy surfaces. Elucidating the complex reactions of polyatomic molecules is one of the most important tasks of theoretical and experimental studies of chemical dynamics. This paper describes our recent experimental studies of the multidimensional multisurface dynamics of polyatomic molecules based on two-dimensional ion/electron imaging. It also discusses ultrafast photoelectron spectroscopy of liquids for elucidating nonadiabatic electronic dynamics in aqueous solutions. 相似文献
14.
M.-C. Heitz G. Durand F. Spiegelman C. Meier 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2003,24(1-3):181-184
The excited state dynamics of the
Na2F cluster initiated by a femtosecond
laser pulse is studied considering a thermally excited initial
sample. Within a pump-probe set-up, the time-dependent
photoelectron spectrum is calculated, which is shown to be a
sensitive tool to study intramolecular motion of the cluster.
Temperature effects are taken into account through thermal
averaging over the time-dependent spectra obtained from
different initial vibrational states of the cluster. The nuclear
motion upon laser excitation is described by full-dimensional
quantum wavepacket propagation using explicit, realistic pump
and probe pulses. The characteristic features of the
time-resolved photoelectron spectra of the
Na2F cluster, identified as due to
periodic bending motion of the cluster as well as to the
excitation of the stretching mode, are found to be robust
against increasing vibrational temperature of the cluster beam.
This finding is important for possible future experiments. 相似文献
15.
Ping He Rongwei Fan Deying Chen Xiaohui Li Yuanqin Xia Xin Yu Yong Yao 《Optics & Laser Technology》2011,43(8):1458-1461
In this paper, ultrafast time-resolved coherent degenerate four-wave-mixing (DFWM) spectroscopy is performed to investigate molecular dynamics in the gaseous phase. Laser pulses lasting for 40 fs are used to create and monitor different vibrational eigenstates of iodine at room temperature (corresponding to a low saturation pressure of about 35 Pa). Using an internal time delay in the DFWM process resonant with the transition between the ground X-state and the excited B-state, the vibrational states of both the electronically excited and the ground states are detected as oscillations in the DFWM transient signal. The dynamics of either the electronically excited or ground state of iodine molecules obtained are consistent with the previous high temperature studies on the femtosecond time-resolved DWFM spectroscopy. 相似文献
16.
Recent advances in the study of quantum vibrations and rotations in the fundamental hydrogen molecules are reported. Using the deuterium molecules (D2+ and D2) as exemplars, the application of ultrafast femtosecond pump-probe experiments to study the creation and time-resolved imaging of coherent nuclear wavepackets is discussed. The ability to study the motion of these fundamental molecules in the time-domain is a notable milestone, made possible through the advent of ultrashort intense laser pulses with durations on sub-vibrational (and sub-rotational) timescales. Quantum wavepacket revivals are characterised for both vibrational and rotational degrees of freedom and quantum models are used to provide a detailed discussion of the underlying ultrafast physical dynamics for the specialist and non-specialist alike. 相似文献
17.
A. Bartelt S. Minemoto C. Lupulescu Š. Vajda L. Wöste 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,16(1):127-131
We have performed adaptive feedback optimization of phase-shaped femtosecond laser pulses to control the wavepacket dynamics
of small mixed alkali-metal clusters. An optimization algorithm based on Evolutionary Strategies was used to maximize the
ion intensities. The optimized pulses for NaK and Na2K converged to pulse trains consisting of numerous peaks. The timing of the elements of the pulse trains corresponds to integer
and half integer numbers of the vibrational periods of the molecules, reflecting the wavepacket dynamics in their excited
states.
Received 4 December 2001 相似文献
18.
The ultrafast dynamics of the internal conversion of S1 azulene and the excited-state intramolecular proton transfer in 2-(2′-hydroxyphenyl)benzothiazole (HBT) were investigated by pump–probe spectroscopy with tunable pulses as short as 20 fs. In
both cases we find very pronounced oscillatory contributions to the transients, which are due to vibrational wavepacket motion
in the excited state. The damping times are on the order of 1 ps even for these large reactive molecules in solution at room
temperature. For azulene only 2 out of 48 vibrational modes participate and in HBT only 4 out of 69. This high degree of localization
of the wavepacket seems to be a general feature, and supports hopes that even for systems of chemical interest coherent control
might be possible.
Received: 24 January 2000 / Published online: 24 July 2000 相似文献
19.
Srinivasa Rao Karumuri Joydeep Choudhury Nirmal Kumar Sarkar Bandana Gogoi Ramendu Bhattacharjee 《Indian Journal of Physics》2010,84(6):647-652
Porphyrins have received numerous considerable attentions during recent years because of their great biological importance.
The most interesting areas of current research in molecular spectroscopy are the study of the vibrational ground and excited
states of polyatomic molecules especially for the Metalloporphyrins. In this paper, we have calculated the fundamental and
extrapolated vibrational energy levels of Magnesium, Nickel, Copper, Zinc, Metalloporphyrin molecules using U (2) algebraic
model Hamiltonian. The results obtained by this method are in good agreement with the experimental data. This study gives
a general approach for solving the vibrational spectra of Metalloporphyrin molecules. 相似文献