APPLICATION OF ASSOCIATIVE IONIZATION TO THE OBSERVATION OF QUANTUM BEATS IN LOW-LYING ATOMIC RESONANCES

A method is described which allows the detection of atomic quantum bea ts or wave-packet evolution in low-lying states, phenomena which are u sually difficult to observe. The excitation method consists of a phase -sensitive two-pulse technique. Detection of the excited-state populat ion after the two pulses is achieved by monitoring rubidium dimer ions which are formed in the associative ionization reaction, Rb(n)p + Rb --> Rb-2(+) + e(-). The dimer ion yield as a function of the waveleng th showed strong features, which coincided with the 8p to 15p atomic r esonances. The two-pulse technique revealed atomic fine-structure quan tum beats due to the coherent excitation of the np(2)P(1/2,3/2) fine-s tructure states of the atom.