Quantum beats observed in photoionization

Quantum beats of the hyperfine levels of the 3 2 P 3 2 state of sodium have been observed in photoionization. The atoms are ionized stepwise with two pulsed lasers. The photoelectron angular distribution, measured as a function of the delay between the two laser pulses, exhibits a periodic variation due to the quantum beat effect. The hyperfine splitting of the intermediate state estimated from these measurements is in good agreement with literature values.