Stark effect higher order

By taking into account the matrix elements off diagonal in n, the second and higher order contributions to the Stark effect can be calculated. If the calculation is carried through second order, the energies are given by1... 

The Stark effect requires the application of electric fields of the order of 10 Vcm or higher. The electrochemical interface, where molecules and ions are subjected to fields in the order of 10 Vcm S seems to be the ideal place to study this phenomenon. 

Higher-Order Stark Effect on Magnetic Fine Structure of the Helium Atom... 

Note that the Hamiltonian (237) is a good approximation for the one- and two-photon processes (as shown in Section III.E for the two-photon case), but that it is only a rough approximation for higher multiphoton processes, since the Stark shifts should contain additional terms of higher order to be consistent with the order of the effective Rabi frequency. 

On the basis of the same device and technique, Koch precisely measured the intense-field Stark effect in highly excited states of atomic hydrogen. Atoms in the n = 10 state, produced by + Xe electron transfer collisions, were excited to the = 25 and n = 30 states with a CO2 laser at A = 10/um. It was demonstrated that the Rayleigh-Schrodinger perturbation theory does not describe the experimental results properly. After a convergent behavior up to a certain order, the theory diverges for higher orders. 

We now address the question how much atomic physics needs to be included in order to account for ATI In fig. 9.6, we show experimental data for ATI from [493], obtained at several laser intensities. One of the important properties of ATI peaks, referred to as peak suppression, is that the relative intensity of the first ATI peaks above threshold does not increase uniformly with laser field strength, but actually begins to decrease in intensity relative to higher energy peaks as the laser field strength increases. Such behaviour cannot be explained in a perturbative scheme, in which interactions must decrease monotonically order by order as the number of photons involved increases, but can be accounted for in terms of the AC Stark shift of the ionisation potential in the presence of the laser field. In ATI experiments, the ionisation potential appears to shift by an average amount nearly equal to the ponderomotive potential, so that prominent, discrete ATI peaks are seen despite the many different intensities present during the laser pulse. However, ATI peaks closest to the ionisation limit become suppressed as the amplitude of the laser field oscillations increases and the ionisation threshold sweeps past them (a different effect which also suppresses ionisation near threshold is discussed in section 9.24.1). 

The situation is simpler for the first-order desorption systems since, in that case, only the desorption energy is affected by lateral interactions the criterion of occupied nearest sites being essential for desorption is not needed. An example of the effect of attractive lateral interactions on desorption can be seen in Fig. 36, taken from the work of Jones and Perry [457] on the Hg/W 100 system. These workers initially concluded that the desorption was zero order [457] since, as Fig. 36 shows, the peak temperature shifts to higher temperature with increasing coverage. However, this conclusion was in stark contrast to the adsorption heat with increasing coverage. Subsequently, Jones and Perry [458] intepreted their... 

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