Optimal laser control of molecular photoassociation along with vibrational stabilization

Nonlinear photoassociation through exotic orbits

We investigate the effects of a particular kind of orbits, which we call exotic orbits, on the process of classical molecular photoassociation. As a starting model system, we consider the process described by the Morse potential with a time-dependent perturbation consisting of the interaction of an external laser field with the molecular dipole. When the external perturbation is turned off, the bound molecular states are classically represented by librational motion, whereas the unbound, the collisional states, are represented by unbound motion, and in both cases, the energy is a constant of motion. When the perturbation is turned on, the total energy is no longer a constant of motion and initial conditions in the unbound region can reach the bound region, and vice versa, through chaotic orbits. Alternatively, we have found that the connection between the bound and unbound sectors can be achieved through exotic orbits, which are comprised by librationlike parts, a localized chaotic region, and an unbounded constant-energy part. Thus, if a colliding atomic pair is in an exotic orbit, it penetrates a chaotic region coming from the unbound sector, subsequently performing librationlike motion, during which the molecule with constant bound energy is formed. Afterwards, the molecule returns to the chaotic region and from this region, it can either access a distinct bound energy or dissociate. We call this phenomenon, in which a metastable molecule is formed, intermittent photoassociation. We show that the key for the emergence of exotic orbits is the relatively short range of the dipole as compared to the interacting potential range. In order to further verify our results, we have considered realistic forms for the potentials and dipole functions of several molecules and found the emergence of exotic orbits, and consequently of intermittent photoassociation, for the MgLi and SrLi molecular parameters.

Electronic Structure with Dipole Moment and Rovibrational Calculation of Cadmium Chalcogenide Molecules CdX (X = Se, Te)

Ab initio calculations of 51 electronic states in the representation 2s+1Λ(±) of CdX (X = Se, Te) molecules have been carried out by using the complete active space self-consistent field and multireference configuration interaction (single and double excitations with the Davidson correction). The potential energy along with the static and transition dipole moment curves for the investigated electronic states of the CdX molecules has been mapped. Consequently, the spectroscopic constants R e, ωe, B e, and T e have been computed for the bound states. The spectroscopic dissociation energy D e, the zero-point energy, and the ionicity are also calculated for the bound electronic states X3Π, (1)1Σ+, (1)1Π, and (1)3Σ+. Rovibrational calculation is performed for the X3Π, (1)1Σ+, (1)1Π, and (1)3Σ+ states of CdSe together with the X3Π, (1)1Σ+, and (1)1Π states of a CdTe molecule. The Einstein coefficients of spontaneous and induced emissions, A 21 and B 21, are computed for the transition between the electronic states (1)3Σ+ and X3Π. In the present work, the values are well-consistent with those available in the literature.

Electronic structure with dipole moment and ionicity calculations of the low-lying electronic states of the ZnF molecule

Adiabatic potential energy curves of the 28 low-lying doublet and quartet electronic states in the representation 2s+1Λ(±) of the zinc monofluoride molecule are investigated using the complete active space self-consistent field (CASSCF) with multi-reference configuration interaction (MRCI) method including single and double excitations with the Davidson correction (+Q). The internuclear distance Re, the harmonic frequency ωe, the static and transition dipole moment μ, the rotational constant Be, and the electronic transition energy with respect to the ground state Te are calculated for the bound states. The transition dipole moment between some doublet states is used to determine the Einstein spontaneous A21 and induced emission [Formula: see text] coefficients, as well as the spontaneous radiative lifetime τspon, emission wavelength λ21, and oscillator strength f21. The ground state ionicity qionicity and equilibrium dissociation energy DE,e are also computed. The comparison between the values of the present work and those available in the literature for several electronic states shows very good agreement. Twenty-three new electronic states have been studied in the present work for the first time.

Sampling-based robust control in synchronizing collision with shaped laser pulses: an application in charge transfer for H+ + D → H + D+

In this paper, we show that robust laser pulses can be obtained by a sampling-based method to achieve a desired charge transfer probability with limited sensitivity to the arrival time of laser pulses.

The X (X = F, Cl, I) effect on the photoassociation of H+X→HX

This work explores the vibrational state-selective photoassociation (PA) in the ground state of the HX (X = F, Cl, I) molecule by solving the time-dependent Schrödinger equation. For the three systems, the vibrational level of [Formula: see text] is set to be the target state and the PA probability of the target state is calculated and compared by considering different initial collision momentums. It is found that the PA probabilities are in accordance with Franck–Condon overlap integral for the HI and HCl systems, but it is not the case for the HF system. Moreover, for the HF system, it is shown that the PA probability of the target state is largest and the multiphoton transition is more likely to occur.

Optimal control of charge transfer for slow H+ + D collisions with shaped laser pulses

We show that optimally shaped laser pulses can beneficially influence charge transfer in slow H(+)+D collisions. Time-dependent wave packet optimal control simulations are performed based on a two-state adiabatic Hamiltonian. Optimal control is performed using either an adaptive or a fixed target to obtain the desired laser control field. In the adaptive target scheme, the target state is updated according to the renormalized fragmentary yield in the exit channel throughout the optimization process. In the fixed target scheme, the target state in the exit channel is a normalized outgoing Gaussian wave packet located at a large internuclear separation. Both approaches produced excellent optimal outcomes, far exceeding that achieved in the field-free collisional charge transfer. The adaptive target scheme proves to be more efficient, and often with complex final wave packet. In contrast, the fixed target scheme, although more slowly convergent, is found to produce high fidelity for the desired target wave packet. The control mechanism in both cases utilizes bound vibrational states of the transient HD(+) complex.