| Summary: | 博士 === 國立成功大學 === 物理學系碩博士班 === 96 === Atomic and molecular spectroscopy is one of the most fundamental techniques which reveal
the physics described by the quantum mechanics. Therefore, investigations of the spectroscopic characteristics on both samples have attracted considerable attention over the past decades. Hence, the quantum interference phenomenon of the cesium atom and the interaction between
atoms of the sodium diatomic molecule were explored in his work. Three topics of the Cesium atomic spectroscopy regarding on the quantum interference are in this thesis. First, the investigation clarifies the transition between the coherent population trapping and Raman absorption in a ladder-type system of Doppler-broadened cesium vapor. A ompetition window of thistransition due to the probe Rabi frequency was found to be as narrow as 2 MHz. For a weak
probe, the spectrum of electromagnetically induced transparency (EIT) associated with quantum interference suggests that the e®ect of the Doppler velocity on the spectrum is negligible. When the Rabi frequency of the probe becomes comparable with the effective decay rate, an
electromagnetically induced absorption (EIA) dip emerges at the center of the power broadened EIT peak. While the Rabi frequency of the probe exceeds the e®ective decay rate, decoherence that is generated by the intensified probe field occurs and Raman absorption dominates the interaction process, yielding a pure absorption spectrum; the Doppler velocity plays an important
role in the interaction. A theory that is based on density matrix simulation with or without the Doppler effect can qualitatively fit the experimental data. The coherence of atom-photon interactions is created or destroyed using the probe Rabi frequency as a decoherence source. Secondly, doubly dressed states in a ladder-type two-photon, three-level coupling system are observed. The doublet signal of EIT is interpreted as arising from the absorption and gain
components of the Mollow spectrum. The separation of the EIT doublet matches the theoretical prediction. A numerical simulation demonstrates that the Doppler velocity group may perturb the light shift from the symmetric center of the EIT doublet. The quantum nature of
the EIT system signi‾cantly suppresses Doppler broadening. The third, subnatural linewidth in an optical transition on Cs was obtained by the suppression and recovery of the trapping of atoms. Cold Cs atoms in a magneto-optical trap (MOT) were irradiated using a weak probe laser to suppress MOT loading. When a counter-propagating coupling laser was directed to be resonant with the upper transition, the probe laser was induced to transmit and the MOT loading was recovered. This work investigates quantitatively this behavior by applying simulated electromagnetically induced transparency, taking into account the linewidth of the lasers as a decoherence source. Additionally, the experimental observations of the lambda-doubling and
the L-uncoupling of the sodium dimer were discussed in this thesis. The lambda-doubling in Na2
5spg and 5sdg states has been measured using cw high-resolution optical-optical double resonance (OODR) spectroscopy. The lambda-doubling constants depending on both the vibrational and rotational quantum numbers have been derived. Normally, the lambda-doubling separations of
the delta states are much smaller than those of the pistates. However, the constants of the 5sdg
state are much lager than those of the B state. This attributes to the L-uncoupling. At the high-lying Rydberg states, the farther the most outer electron moves apart from its nuclei, the weaker the electronic angular momentum L couples to its internuclear axis. To the limit
of L-uncoupling, the Hund's coupling cases(d) applies. The transition of the Hund's coupling cases due to L-uncoupling removes the degeneracy of Lambda-doubling in the Na2 5sdg state. This makes the separation of lambda-doubling in the high-lying delta states larger than those in the lower pi states. The first order of lambda-doubling constants in the Na2 5sdg, 5spg states are experimentally
measured and are significantly larger than those in the B state. This splitting is affected by the perturbations between the adjacent states as well as the L-uncoupling from its internuclear axis.
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