分子近阈结构的理论研究

本文利用多重散射方法研究了分子的近阈结构,阐明了:1)激发电子与分子离子实的相互作用动力学特征;2)势形共振的物理起源。并与实验比较,标识了NO₂内壳层激发的实验谱。 关键词：     

Phase diagram of the Holstein polaron in one dimension

The behavior of the 1D Holstein polaron is described, with emphasis on lattice coarsening effects, by distinguishing between adiabatic and nonadiabatic contributions to the local correlations and dispersion properties. The original and unifying systematization of the crossovers between the different polaron behaviors, usually considered in the literature, is obtained in terms of quantum to classical, weak coupling to strong coupling, adiabatic to nonadiabatic, itinerant to self-trapped polarons and large to small polarons. It is argued that the relationship between various aspects of polaron states can be specified by five regimes: the weak-coupling regime, the regime of large adiabatic polarons, the regime of small adiabatic polarons, the regime of small nonadiabatic (Lang-Firsov) polarons, and the transitory regime of small pinned polarons for which the adiabatic and nonadiabatic contributions are inextricably mixed in the polaron dispersion properties. The crossovers between these five regimes are positioned in the parameter space of the Holstein Hamiltonian.     

Nonadiabatic fragmentation of excited molecular ions: An exploratory study for

The photodissociation of was studied in a one-dimensional approximation, with the aim of understanding the nonadiabatic features of the fragmentation dynamics. In the collinear arrangement of the system, the three lowest excited surfaces (states) interact via two avoided crossings outside the Franck-Condon region, and they are strongly coupled radially by nonadiabatic terms. Electronic transition probabilities for the process , with in one of the three lowest electronic states involved in the fragmentation, were calculated using the semiclassical multichannel S-matrix within the half-collision approach to photodissociation. The reliability of the semiclassical theory, for treating multichannel nonadiabatic processes was analyzed, and inelastic cross-sections for the three processes of electronically selected fragmentations were calculated. The structure found in the calculated absorption lineshapes reveals the marked influence of the nonadiabatic couplings between excited states in the fragmentation dynamics of this molecular ion. Received: 6 March 1998 / Revised: 7 March 1998 and 17 June 1998 / Accepted: 23 June 1998     

Intramolecular interactions and deuteration effect in nonradiative deactivation of lowest triplet state of anthracene and naphthalene

In the approximation of nonadiabatic interactions and considering all out-of-plane vibrational modes to be promoting ones, we calculate changes in the rate constants T _s K _dg ^s of the nonradiative degradation T ₁ ^s ⇝ S ₀ of in-plane spin (s) triplet states as a result of the complete deuteration of anthracene and naphthalene molecules. We examine how the deuteration, the frequency factor, and the shape of promoting vibrational modes affect the squared matrix elements of both nonadiabatic coupling and adiabatic vibronically induced spin-orbit (VISO) coupling of electronic states. The compensation effect of spin-orbit interactions in structural elements of the carbon backbone of the anthracene molecule is ascertained.     

Low-Lying Doubly Excited States of the Helium Isoelectronic Series

We present within the hyperspherical adiabatic approach a nonadiabatic calculation of the low-lying doubly excited states for heliumlike atomic systems with Z ranging from 2 to 6. Potential curves, channel functions, and nonadiabatic couplings are accurately obtained using a well-established technique. By neglecting the lowest potential curve of each system, the doubly excited states are identified as bound states of the remaining coupled closed channels. We investigate the efficacy of this approximation by comparing the resonance positions with the values obtained when the coupling with the neglected open channel is included in the calculation.Received September 23, 2002; accepted November 6, 2002 Published online June 27, 2003     

S3解离中的非绝热过程

采用量子力学从头计算方法研究了硫的三聚物S_３低激发态解离过程.构造了S_３分子的解离极限.对态态间跃迁极矩的计算表明，在势能曲面的交叉区域态态间存在相互转换的非绝热过程，从而确定了在S_３解离为S₂的复杂过程中，非绝热预解离是重要的解离通道. 关键词： ３')" href="#">S_３ 从头算 预解离 非绝热     

The Mechanism of Magnetically Tuned Singlet-Triplet Avoided Crossings in the Ã(1)A(2)-&Xtilde;(1)A(1) 4(1)(0) Band of Thioformaldehyde H(2)C&dbond;S

Magnetically tuned singlet-triplet perturbations in the 4(1)?(1)A(2)-2(1)3(1)?(3)A(2) system of thioformaldehyde, found in ortho-rotational states (I = 1, the two hydrogen spins parallel) have been identified as being caused by vibronic spin-orbit coupling. This perturbation mechanism has been confirmed in several avoided crossings observed in this work for para states (I = 0, hydrogen spins antiparallel) which are much stronger. Parametrization of the theory has led to a quantitative understanding of the experimental frequency-field relations, and to an accurate prediction of the rovibrational energies of the triplet state. This in turn permitted the detection of about 100 Doppler-limited 2(1)3(1)?(3)A(2)-0(0) &Xtilde;(1)A(1) rovibronic transitions which led into fine structure states. The combined data was then used to determine a set of rotational, fine, and hyperfine triplet-state parameters, the term value T(0)(2(1)3(1)?(3)A(2)) = (16 685.385 +/- 0.002) cm(-1), and the spin-orbit vibronic singlet-triplet coupling constant, W(ST) = (0.0691 +/- 0.0016) cm(-1). A large number of frequency perturbations observed in the crossings, ranging from 2 to 300 MHz, can be explained with this single parameter. Copyright 2000 Academic Press.     

The effect of a heavy atom on the nonradiative intersystem crossing transition between ππ<Superscript>*</Superscript> excited states

The effect of a heavy atom on the rate of the nonradiative intersystem crossing transition S ₁(ππ^*) ? T(ππ^*) in molecules of polychlorinated dioxins and dibenzofuran is theoretically studied in the approximation of spin-orbit and nonadiabatic interactions coupling electronic states.     

非绝热分子动力学的量子路径模拟

基于近期发展的经典-量子混合模拟非绝热分子动力学的量子路径方案,本文对5个典型势能面模型进行了模拟,包括单交叉模型、双交叉模型、拓展耦合模型、哑铃模型以及双弓模型.由于难以在严格意义上得到退相干速率,数值模拟中,我们比较了三个不同的退相干速率公式,包括冻结高斯波包近似退相干速率、能量分辨速率以及力分辨速率.在模拟过程中,我们恰当地处理了势能面跳跃时的能量守恒和力的反向问题.通过与全量子动力学模拟的精确结果进行对比发现,对于结构较简单的势能面模型,三种退相干速率都能得到较好的结果;然而对于较复杂的势能面模型,由于复杂量子干涉的原因,与其他混合经典-量子动力学方案类似,量子路径方案仍然难以得到较准确的结果.如何发展更加有效的混合经典-量子模拟方案,是未来研究的重要课题.     

Nonadiabatic effects in (1~2)<Superscript>1</Superscript>Π–X<Superscript>1</Superscript>Σ<Superscript>+</Superscript> rovibronic transitions of KRb molecules

Numerical simulation of the effect of intramolecular electrostatic interactions on redistribution of relative intensities in the vibrational structure of (1 ~ 2)¹Π–X¹Σ⁺ rotationally resolved transitions of the KRb molecule is performed within the precision nonadiabatic model of coupled vibrational channels. It is established that mutual perturbation of electronically excited states modifies in a nontrivial way a nodal structure of nonadiabatic wavefunction of the (1 ~ 2)¹Π complex, which is possible to use for rising efficiency of twostep laser synthesis and stabilization of ultracold ensembles of KRb molecules in the ground electronic state.     

Optical clock with millihertz linewidth based on a phase-matching effect

We propose a new scheme for the optical frequency standard based on the phase-matching effect of the nonadiabatic interaction of two quasimonochromatic fields with the states 1S0, 1P1, and 3P0 of atoms 88Sr, which are trapped in an optical lattice with magic wavelength. After establishing the phase correlation between two laser fields by the nonadiabatic process, the final linewidth for the difference frequency field, which can be generated by a nonlinear optical crystal, is about 1 mHz.     

ns6s里德堡分子的势能曲线

里德堡电子与基态原子的低能电子散射形成长程里德堡分子,这种分子具有大的轨道半径,丰富的振动能级和永久电偶极矩等特点。本文考虑铯里德堡ns态与(n-4)l(n为主量子数,l为角量子数且l2)近简并态的非绝热耦合与p-波共振现象,数值计算了长程铯里德堡分子的势能曲线。分析ns6s(n=32-36)态分子最外层势阱,研究了长程里德堡分子的势阱深度、平衡距离与主量子数n的关系,为实验研究长程里德堡分子提供理论依据。     

Atoms in a radio-frequency-dressed optical lattice

We load cold atoms into an optical lattice dramatically reshaped by radio-frequency coupling of state-dependent lattice potentials. This radio-frequency dressing changes the unit cell of the lattice at a subwavelength scale, such that its curvature and topology departs strongly from that of a simple sinusoidal lattice potential. Radio-frequency dressing has previously been performed at length scales from mm to tens of mum, but not at the single-optical-wavelength scale. At this length scale significant coupling between adiabatic potentials leads to nonadiabatic transitions, which we measure as a function of lattice depth and dressing amplitude. We also investigate the dressing by measuring changes in the momentum distribution of the dressed states.     

Perturbation of the radiative lifetimes of rovibronic levels of the nl complex of terms of a diatomic molecule

Within the framework of a sufficiently general nonadiabatic model taking into account the interaction of an arbitrary finite number of electronic states and not requiring the smallness of a perturbation parameter, expressions have been obtained for the radiative lifetimes of the rovibronic levels of states of the nl complex of terms of a diatomic molecule. It is shown that the determination of ratios of the nonadiabatic and adiabatic radiative lifetimes for the rovibronic levels can be reduced to the solution of two independent problems (the determination of ratios of the adiabatic values of radiative lifetimes for the mutually perturbing states and determination of the expansion coefficients of the wave functions of rovibronic states in the Born-Oppenheimer basis set of wave functions) when the rovibronic states are perturbed by only a single rovibrational level of each electronic state or by an arbitrary number of rovibrational states of each electronic state provided that the potential curves of the combining states are similar and the dipole moments of electronic transitions weakly depend on the internuclear separation (which is quite a case for highly excited electronic states). To illustrate the efficiency of using the expressions obtained, the perturbations of the radiative lifetimes of rovibrational levels of the I ¹Π _g ^? and J ¹Δ _g ^? states of the 3d complex of terms of the H₂ molecule were considered.     

Initial conditions of the universe: how much isocurvature is allowed?

We investigate the constraints imposed by current data on correlated mixtures of adiabatic and nonadiabatic primordial perturbations. We discover subtle flat directions in parameter space that tolerate large (approximately 60%) fractions of nonadiabatic fluctuations. In particular, larger values of the baryon density and a spectral tilt are allowed. The cancellations in the degenerate directions are explored and the role of priors is elucidated.     

Families of spatial solitons in a two-channel waveguide with the cubic-quintic nonlinearity

We present eight types of spatial optical solitons which are possible in a model of a planar waveguide that includes a dual-channel trapping structure and competing (cubic-quintic) nonlinearity. The families of trapped beams include “broad” and “narrow” symmetric and antisymmetric solitons, composite states, built as combinations of broad and narrow beams with identical or opposite signs (“unipolar” and “bipolar” states, respectively), and “single-sided” broad and narrow beams trapped, essentially, in a single channel. The stability of the families is investigated via the computation of eigenvalues of small perturbations, and is verified in direct simulations. Three species-narrow symmetric, broad antisymmetric, and unipolar composite states-are unstable to perturbations with real eigenvalues, while the other five families are stable. The unstable states do not decay, but, instead, spontaneously transform themselves into persistent breathers, which, in some cases, demonstrate dynamical symmetry breaking and chaotic internal oscillations. A noteworthy feature is a stability exchange between the broad and narrow antisymmetric states: in the limit when the two channels merge into one, the former species becomes stable, while the latter one loses its stability. Different branches of the stationary states are linked by four bifurcations, which take different forms in the model with the strong and weak coupling between the channels.     

Experimental and numerical study on the basin stability of the coupled metronomes

The basin stability is an effective parameter to measure the stability of multistable system under perturbations. In this paper, we try to explore the effects of the coupling strength on the basin stability of the coupled metronomes. In two coupled non-identical metronomes, the coupling strength linearly decreases the basin stability of in-phase synchronization while increases that of the anti-phase synchronization. In three coupled metronomes, there are rich coexisting collectively dynamics as in-phase, anti-phase synchronization, quasi-period states and period 4 states. The coupling strength may still change the basin stability of these coexisting dynamics states. The results are observed in experimental systems and numerical models. Our findings are significant on understanding the multistable dynamics under noisy environment.     

The A (3Pi1) State of ClF

The A(3Pi1) state of ClF is studied (1) in emission from the beta(1(3)P2) ion-pair state in a high-pressure discharge, (2) from its role in perturbations of the B(3Pi0(+)) and A'(3Pi2) states, and (3) in direct absorption from the X(1Sigma+) ground state. The last of these is obtained via a UV-labeling technique and represents the first observation of the A <-- X transition. The emission spectrum yields extensive assignments for the 0-4, 0-5, and 1-4 bands of beta --> A, with both e and f lines identified. The well-known perturbation in v = 7 of the B state is attributed to interaction with v = 9 of A. A newly identified perturbation in B(6) involves coupling with A(8). The known perturbation in B(8) may involve A(11), but other assignments cannot be ruled out. Approximate potential curves are derived for all three valence states and used to compute the vibrational factors for the perturbations, permitting extraction of the electronic coupling strengths. The B-A coupling elements are within approximately 10% of expectations for rotation-electronic coupling within a Hund's case (a) 3Pi manifold, but the strength of the perturbation between A(5) and A'(6) is only about 30% of predictions for this model. Copyright 1999 Academic Press.     

Defects in heavy-fermion materials: unveiling strong correlations in real space

Defects provide important insight into the complex electronic and magnetic structure of heavy-fermion materials by inducing qualitatively different real-space perturbations in the electronic and magnetic correlations of the system. These perturbations possess direct experimental signatures in the local density of states, such as an impurity bound state, and the nonlocal spin susceptibility. Moreover, highly nonlinear quantum interference between defect-induced perturbations can drive the system through a first-order phase transition to a novel inhomogeneous ground state.