The general process in lasers

In F

The atoms at autoionization state can be excited to higher continuum state, as well as transit to bond states by spontaneous emission a photon in laser induced autoionization. The effect of these processes on the laser induced autoionization process has been investigated by means of using the reaction matrix. The effect of spontaneous emission process is small in general case, but its spectrum shows that the emission is contributed mainly from the spontaneous Raman scattering enhanced by the cutoioni-zation state, and the Dressed atom picture was shown clearly. The multiphoton process makes the photoelectron spectra and laser induced autoionization process very complicated. For example, the photoelectron spectra of one and two-photon process have multi-maxium structure.

Halina Abramczyk

K. Wódkiewicz, Joseph H. Eberly

We discuss relations between different jump processes used by us and other workers for the description of external electromagnetic field fluctuations. We show that the shot noise, the random telegraph signal, and the Poisson process are examples of a general class of fluctuations described by the relevant Burshtein-Chapman-Kolmogorov-Smoluchowski equation. We establish general conditions for which all these processes lead to the same atomic response in strong field-atom interactions.

Kōichi Shimoda

Pierre Meystre, Murray Sargent

Xiao‐Min Tong, Naoki Toshima

We propose a theoretical method to calculate the infrared (IR) laser-assisted photoabsorption cross sections over a broad energy range by a single calculation. In this method we define an initial wave function as the product of the dipole operator and the atomic ground state, propagate the initial wave function in the IR laser field with different initial phases, then calculate the generalized autocorrelation function, which is defined as the averaged value of the autocorrelation function over the initial phase from 0 to $2\ensuremath{\pi}$ (or one IR optical cycle). The IR laser-assisted photoabsorption cross sections are obtained by the Fourier transform of the generalized autocorrelation function. We apply this method to study the IR laser-assisted photoabsorption of He atoms. From the simulation results, we see that the IR laser field affects not only the resonant position but also the lifetime or the width of the bound states. This photoabsorption cross section is an important quantity to analyze the IR-laser-assisted dynamical processes by an attosecond pulse, a pulse train, or a free-electron laser.