l-mixing dynamics of Rydberg states of hydrogen atom in a static electric field

Both exact analytical formula and numerical calculations are performed to study the l-mixing population decay of the n = 10 and n = 100 high Rydberg states of hydrogen atoms in an electric field. The two time constants of and observed in zero-electron-kinetic-energy (ZEKE) experiments in the common stray field condition, i.e. - can be obtained by 2-exponential fitting of the exact decay curve. The principle of high-resolution ZEKE spctroscopy based on the two time constants is then elucidated. The inverse Born-Oppenheimer approximation will be introduced to treat the ZEKE states of complex systems like many-electron atoms, molecules, clusters etc.