波包动力学-飞秒激光操纵波包过程

本文介绍了波包动力学的基本理论和数值模拟方法,尤其是在飞秒激光与分子相互作用领域中的应用,探讨了飞秒激光引起的波包过程（包括波包的制备、波包的干涉）,以及利用调频脉冲、脉冲串和优化脉冲形状控制波包动力学的方案。     

波包动力学-飞秒激光操纵波包过程

本文介绍了波包动力学的基本理论和数值模拟方法,尤其是在飞秒激光与分子相互作用领域中的应用,探讨了飞秒激光引起的波包过程（包括波包的制备、波包的干涉）,以及利用调频脉冲、脉冲串和优化脉冲形状控制波包动力学的方案。     

NaLi分子飞秒含时光电子能谱的理论研究

运用三态模型和含时波包方法,研究了NaLi分子处于强飞秒抽运-探测激光场中的波包动力学过程和时间分辨光电子能谱,并且揭示了飞秒激光脉冲参数与NaLi分子光电子能谱之间的关系.研究发现:对于不同的激光波长,波包的振动周期是不同的,而且随着抽运-探测脉冲延迟时间的不同,NaLi分子光电子能谱的谱峰高度和位置发生变化;当λ1=352 nm并且?t=400 fs时,外阱中相应的光电离信号(0.5 eV处)明显强于内阱中相应的光电离信号(1.35 eV处).计算结果表明,NaLi分子激发态41Σ+上波包动力学的一些信息能够通过其光电子能谱反映出来.这些结果可以为实验上实现分子的光控制以及量子操控过程提供一些有价值的参考信息,并为进一步的理论研究提供重要依据.     

Time-dependent wave packet theoretical study of femtosecond photoelectron spectra and coupling between the A<Superscript>2</Superscript>Σ<Superscript>+</Superscript> and B<Superscript>2</Superscript>Π states of the NO molecule in a strong laser field

In this work, the femtosecond time-resolved photoelectron spectra and the coupling between the A²Σ⁺ and B²Π states of the NO molecule in a strong laser field have been investigated by the time-dependent wave packet method. We demonstrate that the weak coupling between the A²Σ⁺ and B²Π states of NO plays a key role on the peak centered at 0.37 eV of the photoelectron spectra in the 2+1’ channel.     

激光场强度对NO电子态粒子数布居影响的理论研究

用含时波包方法研究了激光场强度对NO各电子态上粒子数布居的影响.在计算中,采用了四态模型.利用分裂算符傅里叶变换方法求解Schrdinger方程,得到各个电子态的波函数,从而求得各个电子态上粒子数的布居.计算结果表明,不同强度的抽运光对各个电子态上粒子数布居会产生不同的影响.通过改变激光强度可以实现对电离产率的控制,这种思想对实现原子分子过程的激光操控具有重要意义.     

Predissociation and photodissociation of IBr

The observed predominance of excited Br(² P _1/2) atoms in the nearultra-violet photodissociation products of IBr is shown to be quantitatively consistent with an intermediate coupling regime in the visible absorption region, which invalidates the traditional interpretation of the B′(O ⁺) state as a new Born-Oppenheimer state arising from a strongly avoided potential curve crossing. A general theory of predissociation at intermediate coupling, covering the positions, intensities and widths of the spectral lines, shows that both diabatic and adiabatic characteristics must be taken into account. The presence of a sharp level is predicted at any coincidence between an adiabatic and a diabatic term value with the same J value, and the spacing between neighbouring lines is shown to depend on an average between the diabatic and adiabatic rotational constants. The theory is successfully applied to the B(³Π _{o ⁺} ) and B′(O ⁺) states of IBr, and potential curves for the two states are reported. The analysis is consistent with the following curve crossing parameters r_x = 3·220 Å, E_x = 16 915 cm^-1, V ₁₂ = 170 cm^-1, and ΔF = 9178 cm^-1 Å^-1, and with the following spectroscopic constants for the B′(O ⁺) state of IBr⁷⁹:

     

Unravelling the visible spectrum of strontium monomethoxide

The bands of the A²E–X²A₁ and B²A₁–X²A₁ electronic transitions of SrO¹²CH₃ and the B²A₁–X²A₁ transition of SrO¹³CH₃ have been recorded at high resolution using a laser ablation jet source. The optical–optical double resonance population depletion technique was used to facilitate the assignment of the spectra. Rotational levels with K = 0, ±1 in the X²A₁ and B²A₁ states and K = 0, 1 and 2 in the A²E state have all been characterised. A perturbation affecting the B²A₁ state caused a reversal of the ordering of the spin-rotation components, F₁ and F₂, in the SrO¹²CH₃ isotopologue. This required the introduction of a modified rotational constant B_mod, affecting only the K = 1, F₂ component of the B²A₁ state, in order to model the SrO¹²CH₃ data in a global fit of the A²E–X²A₁ and B²A₁–X²A₁ transitions.     

High-resolution LIF measurements on hyperfine structure and isotope shifts in various states of Lu I using the second and third harmonic of a cw Ti:sapphire laser

With the second and third harmonic of a tunable single-mode cw Ti:S laser, generated inside external enhancement cavities, high-resolution LIF measurements on several states of Lu I in various parts of the electromagnetic spectrum are performed. From these measurements, hyperfine structure A and B constants for both ¹⁷⁵Lu and ¹⁷⁶Lu as well as isotope shifts have been determined for all levels observed in the single-step excitation process. From the measured A constants, the magnetic hyperfine structure anomaly has been derived for various states. Received 14 January 2002 Published online 19 July 2002     

Fine structure of the close-lying A 2Π and B 2Σ+ states of BaH and BaD

Molecular parameters for the close-lying and strongly interacting A ²Π and B ²Σ states of BaH and BaD have been re-evaluated by means of a numerical matrix diagonalization procedure. The results obtained according to this exact method deviate considerably from the effective ones of previous investigations, particularly with respect to the A ²Π-B ²Σ⁺ interaction matrix elements which describe the large Λ-doubling and spin-splitting. The new values of the Λ-doubling and spin-splitting parameters are in excellent agreement with pure precession values for L = 2, and thus the present results form an interesting extension of the pure precession model which so far has been found applicable in a number of cases for which L equals one. The pure precession result L = 2 indicates that the outermost electron of the A ²Π and B ²Σ⁺ states must be a d-electron, and this requires a re-assignment of the configuration quantum numbers of these states. Strong local perturbations are observed in the rotational levels of the A ²Π state of both BaH and BaD, and the result L = 2 now yields a further confirmation of the previous assumption that a ²Δ state causes these perturbations. In the case of BaD the electronic + vibrational energy and the rotational constants (B_v , D_v ) of the perturbing level could be determined from the perturbed A ²Π term values, and in particular the value of the interaction matrix element leads to the conclusion that there is a A ²Π, v = 0 - ²Δ, v = 2 interaction. Finally the influence of the A ²Π - ²Δ, Δv = 0 interaction on the A ²Π and B ²Σ⁺ molecular parameters was investigated.     

Control of wavepacket dynamics in mixed alkali metal clusters by optimally shaped fs pulses

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