Coherence narrowing of excited atomic energy levels

Dipankar Bhattacharyya, Jyotirmoy Guha

Mikhail Vladimirovich Fedorov, A. M. Movsesian

Photoionization of highly excited atoms by a strong microwave field is considered. Secondary coherent population of some neighboring Rydberg levels in the process of ionization is shown to be a reason for interference of transitions from these levels to the continuum. Interference is shown to be a reason for some new effects: stabilization of the atom, suppression of its ionization, appearance of a multipeak structure in the photoelectron spectrum, field-induced narrowing of its peaks, narrowing and localization of quasi-energy atomic spectrum in a strong field, etc.

Elijah Ogaro Nyakang’o

Wang Li－Jun, Yu Hui-Ying, 清华大学工程物理系,北京　100084

In this paper the semi-classic theory of coherent excitation of a two-level atom was modified and applied to a two-level atom with a hyperfine structure. The im portant result of calculation is as follows: when the exciting laser power is la rge enough, due to the power broadening effect, a narrow-band laser can excite a two-level atom with a hyperfine structure effectively. So it is not necessary t o use a broad-band laser to guarantee excitation efficiency for an atom with hyp erfine split levels.

Arend Niehaus

Xiaoli Li, Yafang Shi, Lin Liu +6 more

Atomic coherence and interference play an important role in the study of the atom-photon interactions. Electromagnetically induced transparency (EIT) is an extensively studied two-photon coherence phenomenon theoretically as well as experimentally. EIT is mainly observed in three-level atomic systems which causes transparency by quenching absorption of the medium. In this paper, based on the lambda type three-level system including energy level |1>, |2> and |3>, a microwave driving field is introduced between the excited-state energy level |3> and another excited-state energy level |4> to form an inverted Y-type four-level system. We theoretically study the two- and three-photon coherence in this system. The results show that the coupling field makes the probing absorption intensity at the resonant frequency have a very narrow line-width depression, i.e., EIT. The microwave field causes a dynamic Stark splitting of the energy level |3> and induces the Aulter-Townes double peaks. Their frequency interval is exactly equal to the Rabi frequency of the microwave field. The presence of all three fields induces wide window of EIT at the line center owing to the enhanced depression results. The transient evolution is also discussed to understand the optical switching process in the system. Our theoretical study will be helpful to get a deeper insight into the three-photon effects in multilevel systems.