Multiphoton Dissociation Of Diatomic Molecule Research Articles

Classical-quantum correspondence in multiphoton dissociation of diatomic molecules by chirped laser pulses

The classical and quantum dynamics of diatomic molecules driven by chirped laser pulses are investigated, with particular attention given to the dependence of the classical-quantum correspondence on the microscopic parameters of the systems. For this purpose, several molecules with different effective Planck’s constants are employed and their respective results are compared. Based on the bucket dynamics which has been successfully applied to explain the dissociation mechanism, we propose a criterion that determines whether a particular molecule will show a good correspondence between classical and quantum calculations in a given parameter region. It is found that, when the size of the bucket is bigger than the effective Planck’s constant, the classical predictions of dissociation probabilities agree well with the quantum mechanical results.

A DIATOMIC MOLECULE MULTIPHOTON DISSOCIATION IN INTENSE FIELDS

This work deals with the multiphoton dissociation of diatomic molecule in intense IR laser field, the interaction between field and molecules is approximated to that between field and the dipoles. The Ｓｃｈｒ?ｄｉｎｇｅｒ equation is solved by using Close-Coupling method and Floquet theory. Numerical results for molecule HF are given.

Laser induced stabilization and alignment in multiphoton dissociation of diatomic molecules

The two step photodissociation (1 1Σ+g→1 1Σ+u→1 1Πg) transition in Li2 is studied by a coupled equations method. The first transition is assumed weak and selects particular rovibrational states as intermediate states. The second transition is induced by a high intensity infrared laser. The photodissociation yield for different isotopes is investigated as well as the coherence effects in the excited intermediate states produced by the intense field. Stabilization of dressed molecular states and laser induced alignment effects are shown to occur in the photodissociation at high intensities of the second laser. The effect of the polarization of the lasers on the differential cross sections is also discussed.

Multiphoton dissociation of a diatomic molecule: Laser intensity, frequency, and pulse shape dependence of the fragment momentum distribution

We study by an exact method the infrared multiphoton dissociation of a rotationless diatomic molecule and calculate the fragment relative momentum distribution as a function of the laser intensity and frequency, using either a square or smoothly varying pulse shape. The distribution has peaks due to multiphoton transitions. The nature of the peak structure depends on the laser intensity and whether the laser frequency is comparable to (i.e., within 20%) the ν=0 to ν=1 transition frequency (ω10) of the diatomic: If it is the distribution has bands spaced by the photon energy which contain peaks due to transitions from many bound states; if the laser frequency is not comparable to ω10, the distribution consists of isolated peaks spaced by the photon energy, which result from multiphoton transitions from the ground vibrational state. Changing the pulse shape from smoothly varying to square adds additional structure to the distributions. At sufficiently high intensities (1015 W/cm2) the high momentum peaks increase in intensity and the low momentum peaks are suppressed as the laser intensity is increased (this effect is often referred to as peak switching). At high laser intensities and frequencies comparable to ω10, classical mechanical calculations of the fragment momentum distribution give a smoothed out approximation to the quantum results and display a shifting similar to peak switching. Classical mechanics is unable to reproduce the quantum results at low intensities or at frequencies not comparable to ω10.

Comment on ‘‘A time-dependent quantum mechanical theory for multiphoton dissociation of diatomic molecules’’

The rate of dissociation of a diatomic molecule in the presence of an intense infra-red laser field is derived, using a non-perturbative method. The T-matrix elements for absorption from an initial bound state to a dissociative state were calculated. (AIP)

A time-independent quantum mechanical theory for multiphoton dissociation of diatomic molecules

A nonperturbative expression for the rate of dissociation from the ground vibrational state of a diatomic molecule in the presence of an infrared laser field is derived using R-matrix techniques. No rotating wave approximation and no metastable levels are introduced. The result is applied to a model system and to HF to obtain the dependence of multiphoton dissociation rate upon laser frequency and intensity. Dissociation is predicted at fields of order 1013 W/cm2.

Multiphoton dissociation of diatomic molecules at high intensities

A non-perturbative method is used to obtain an analytic expression for the rate of multiphoton dissociation of diatomic molecules as a function of the incident radiation. The two-photon dissociation process is considered as an example.

Multiphoton dissociation of diatomic molecule under the influence of intense laser beam

Transition probability of multiphoton dissociation of diatomic molecule in an intense laser beam has been calculated using a method due to Reiss. Numerical computations are done for the case of hydrogen molecular ion. Natural units have been used here.