Application of associative ionization to the observation of quantum beats in low-lying atomic resonances.

Abstract

A method is described which allows the detection of atomic quantum beats or wave-packet evolution in low-lying states, phenomena which are usually difficult to observe. The excitation method consists of a phase-sensitive two-pulse technique. Detection of the excited-state population after the two pulses is achieved by monitoring rubidium dimer ions which are formed in the associative ionization reaction, Rb*(n)p+Rb \ensuremath{\rightarrow}${\mathrm{Rb}}_{2}^{+}$+${\mathit{e}}^{\mathrm{\ensuremath{-}}}$. The dimer ion yield as a function of the wavelength showed strong features, which coincided with the 8p to 15p atomic resonances. The two-pulse technique revealed atomic fine-structure quantum beats due to the coherent excitation of the ${\mathit{np}}^{2}$${\mathit{P}}_{1/2,3/2}$ fine-structure states of the atom. \textcopyright{} 1996 The American Physical Society.