The energy at which the maximum number of photoelectrons are observed during the ionization of potassium and xenon atoms

The two formulae for the energy at which the maximum number of ejected photoelectrons are detected are examined in this paper; one formula is Emax with non-zero momentum included in both the exponent and the pre-exponent part of the expression, and the other formula is EmaxApp, which represents a previous formula, but approximated for higher-intensity laser fields. We examine which formula gives numerical values that are closest to the experimental values obtained in this area of research concerning tunnel ionization of K and Xe atoms by linearly polarized laser fields. It is found that the formula Emax gives satisfactory results in a wide range of laser field intensities, for both atoms. For an intensity of 4×1012  W cm-2, Emax 9.046 eV in the case of the K atom. In the case of the Xe atom, this Emax value occurs at an intensity of 5×1013  W cm-2. In contrast, in experiments, it has been determined that this Emax value occurs at an intensity of 7.5×1013  W cm-2. The formula for EmaxApp is applicable for higher laser intensities; it is consistent with the formula for Emax in a range of field intensities 1015 -1016  W cm-2.