The effect of laser fields on the NO interaction potentials is obtained by the calculation of time-resolved photoelectron spectrum ͑TRPES͒ using the time-dependent wave-packet method. The calculation not only shows that the overlap of the pump-probe pulses makes some NO molecular ''invisible'' states visible, but also that the coupling strength and the positions of relevant curves change on increasing the laser intensity. These changed potentials affect their dynamical behavior and influence the shape and position of each peak in TRPES. That the coupling strength of relevant potentials can be changed by the field-matter interaction is consistent with our ab initio calculations. The effect of external field on molecular potential, which is often called field-matter interaction, always becomes an intriguing topic of many dynamical calculations ͓1-6͔. In order to investigate the interaction conveniently, the concept of light-induced potential is introduced and applied to study the photoionization and photodissociation of molecules. For example, using the light-induced potential, Garraway and Suominen ͓7͔ and Zavriyev et al. ͓8͔ studied the process of transferring of a wave packet from one molecular potential to another, and gave the result that a laser-induced crossing becomes an avoided crossing with an energy gap increasing with the laser intensity. In the research of the dissociation dynamics of molecules exposed to intense laser fields, Wunderlich et al. ͓9͔ observed the clear experimental signature of light-induced potentials and pointed out that the avoided crossing moves to a smaller internuclear distance with increasing laser frequency. In this work, we calculated the femtosecond pulse time-resolved photoelectronic spectrum ͑TRPES͒ of NO multiphoton ionization ͑MPI͒, which was obtained by Ludowise et al. ͓10͔ in strong laser fields, and found not only the phenomena of the potential shifting and the coupling strength changing, but also the direct way to detect the ''trapped'' molecules because of the potential crossing.In the experiment of Ludowise et al. ͓10͔, an intense femtosecond pump pulse induces a transition and prepares a coherent superposition of eigenstates, i.e., a wave packet, via the two-photon excitation. The dynamics of the wave packet is then probed with a second, time-delay weak pulse ͑Fig. 1͒. The kinetic-energy spectrum of the ejected electron is subsequently analyzed as a function of the delay. To calculate the MPI TRPES of NO molecule, the five-state quantummechanical calculations are performed. Invoking the BornOppenheimer approximation and neglecting the coupling between the core and photoelectron, the Hamiltonian for the vibrational motion of the molecule can be written aswhere R is the internuclear separation, the reduced mass of the molecule, and the potential matrix U(R,t) can be written explicitly as *Author to whom correspondence should be addressed. Email ad-

Based on the 13A″ triplet state the product polarizations for the reactions F + HO → HF + O and F + DO → DF + O are studied by using the quasi-classical trajectory (QCT) method. The four generalized polarization-dependent differential cross-sections (PDDCSs) (2π/σ)(dσ00/dωt), (2π/σ)(dσ20/dωt), (2π/σ)(dσ22+/dωt) and (2π/σ)(dσ21−/dωt) have been calculated in the centre-of-mass frame. The distribution of the angle between k and j′, P(θr), the distribution of the dihedral angle denoting k − k′ − j′ correlation, P(ϕr), as well as the angular distribution of product rotational vectors in the form of polar plots P(θr,ϕr) are calculated. The evident influence of isotope substitution on the product polarization is revealed. This effect may be derived from the different mass factor or the effective potential well depth in the two reactions.

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With the many-body expansion method, an accurate global potential energy surface (PES) is constructed for SiH2+(X2A1) by mapping 4762 ab initio energy points calculated on the multireference configuration interaction level including Davidson corrections with aug-cc-pV6Z Dunning’s basis set. The dissociation energies and equilibrium geometries of SiH+(X1Σ+) and H2(X1Σg+) agree well with the experimental results. The topographical characteristics of all stationary points for the SiH2+(X2A1) PES are discussed in detail and compared with other theoretical and experimental results. In order to verify the validity and usability of the present PES, the dynamics calculations based on the Chebyshev quantum wave packet method are performed for the H(S2)+SiH+(X1Σ+)→Si+(P2)+H2(X1Σg+) reaction. The probabilities, the total integral cross sections, and the rate constants are computed, and the analogies with the corresponding ones of reaction H(S2) + CH+(X1Σ+)→C+(P2) + H2(X1Σg+) are also made. The reasonable dynamical behavior throughout the entire configuration space indicates that the PES is suitable for relevant dynamics investigations and serves as a building block for constructing the PES of larger molecular systems containing Si+/H.