Pulsed laser fields

Two scientific aspects in cluster science have been investigated using pulsed-laser field desorption technique with a considerable degree of success.85 One is the critical numbers, which are the smallest numbers of atoms in multiply charged cluster ions when the ions can still resist being... 

Fig. 2.15 (a) In low temperature pulsed-laser field evaporation of silicon, ions formed are all doubly charged. The energy distributions are very narrow, similar to those found in low temperature field evaporation of metals. However, the onset flight times are always shorter than the calculated values, indicating a photo-excitation effect as will be discussed in Sec.2.2.6. 

In pulsed-laser field desorption of helium from rhodium surfaces, if the... 

For formation of cluster ions in pulsed-laser field evaporation of GaAs, GaP... 

Fig. 3.19 Mass separated energy distributions of pulsed-laser field desorbed 4He+ and ions obtained with the Penn State pulsed-laser ToF atom-probe when the flight path length was 778 cm. Their onset flight times are separated by 34 ns, exactly that calculated from the system constants and their critical ion energy deficits at 5.5 kV.

To understand how wave packets are created by ultra-short pulses, consider a molecule interacting with a pulsed laser field s(t). Figure 12 shows the time evolution of a... 

A numerical method for solving the time-dependent Schrodinger equation for a one-electron atomic system in an intense, short-pulsed laser field is presented. An effective potential formalism is proposed and tested for representing the excitation of the valence electrons in rare gases. Results for ion production yields, photoelectron distributions and harmonic conversion are presented and compared to recent experimental results. 

A many electron atom in an intense, pulsed laser field is a formidable computational problem. This is because the multi-dimensional Hamiltonian... 

The TDSE for hydrogen in a pulsed laser field using the length gauge is... 

In this paper we have shown the method we have developed to study the response of rare gas atoms to intense, short pulse laser fields. Realizing that the electric field of the laser can become as strong as or stronger than the Coulombic interactions between the atomic electrons, we chose an approach which treats all these forces on an equal footing. This led us to find a way to solve explicitly the time-dependent Schrodinger for the evolution of the electronic wave function... 

Ryasnyansky, A., Palpant, B., Debrus, S., Ganeev, R., Stepanov, A., Can, N., Biichal, C., Uysal, S. Nonlinear optical absorption of ZnO doped with copper nanoparticles in the picosecond and nanosecond pulse laser field. Appl. Opt. 44, 2839-2845 (2005)... 

Pulsed laser fields may be represented by a classical external vector potential A(t]) considered as a function of the invariant phase ri = cat — k r. A natural scale for characterizing the intensities is provided by the dimensionless parameter... 

Thus, Floquet theory provides a natural means of studying the dynamics of the response of an atomic system to a pulsed laser field. Indeed, it yields a general framwork for discussing the adiabatic motion of any periodically driven quantum system. If we define a characteristic time St = 6A/(dA/dt) which is the time taken to sweep through the avoided crossing, then one can distinguish between three regimes ... 

Figure C3.2.14. Electron population difference x t) = Pj(t) - PJt) for three electron transfer reactions in the presence of a pulsed laser field. Frequency of the field is tuned to solvent reorganization energy A, = 1 eV and the field strength is such that coupling potential (charge transfer dipole moment times the field strength) is twice the...

S.-M. Wang, S.-L. Cong, K.-J. Yuan, Y.-Y. Niu, Photoionization of NO molecule in two-color femtosecond pulse laser fields, Chem. Phys. Lett. 417 (2006) 164. 

K.C. Kulander, K.J. Schafer, J.L. Krause, Dynamic stabilization of hydrogen in an intense, high-frequency, pulsed laser field. Calculation of photoemission from atoms subject to intense laser fields, Phys. Rev. Lett. 66 (1991) 2601 Phys. Rev. A 45 (1992) 4998. 

Table 6.10 TD-UHF temporal behavior of dipole moment d t) and EUE index N t) for the decacene molecule in the pulse laser field with enveloping function E(t) (all quantities in atomic units)...

Vala, J., Duheu, O., Masnou-Seeuws, F., Pillet, R, and Kosloff, R., Coherent control of cold-molecule formation through photoassociation using a chirped-pulsed-laser field,... 

B. (2007) Some aspects of the silicon behaviour under femtosecond pulsed laser field evaporation. 

Unfortunately, however, the original form of Floquet theorem does not apply to the cases where H is not perfectly periodic. This includes the dynamics under pulsed laser field and/or d3mamics coupled with nuclear motion, which are the cases we are most interested in. In order to apply the Floquet based analyses to such cases, one has to generalize the original formulation. Interestingly, as we will show below, the effects of nonperiodicities can be incorporated in terms of nonadiabatic transitions among Floquet states. 

The following subsections are devoted to illustrative applications of nona-diabatic electron wavepacket dynamics to chemical reactions. By tuning pulse laser fields in a coherent or incoherent sense, one can significantly modulate the electronic transition and subsequent molecular dynamics. The correlation between the nonadiabatic term and laser fields can lead to dramatic change in chemical dynamics, which implies that nonadiabatic dynamics and intense-laser fields should be treated on an equal footing [425, 491, 492, 494], Below we show those examples of the coupling between nonadiabatic interactions and laser fields. 

In this section, we consider the interaction of a two-level system with a resonant (A = 0) pulsed laser field. The RWA Hamiltonian for this system reads... 

The Floquet Schrbdinger Equation for Pulsed Laser Fields... 

Consider a molecular system described by the Hamiltonian operator Ho (r, R) in interaction with a pulsed laser field with slowly varying envelope and frequency. Below, for ease of notation, the dependence of the various operators and wavefunctions on the electronic and nuclear coordinates r and R is dropped. In the semiclassical dipolar approximation, the total Hamiltonian operator of the system reads... 

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