Observation of coherent population trapping in a V-type two-electron system

• Published in: New journal of physics Vol. 17; no. 3; pp. 33044 - 33050
• Main Authors: Singh, Alok K, Natarajan, Vasant
• Format: Journal Article
• Language: English
• Published: Bristol IOP Publishing 31.03.2015
• Subjects: Atomic structure; Coherence; coherent population trapping; Dipping; Electrons; Excitation; Fluorescence; Formations; intercombination line; Lift; Magnetic fields; Physics; Trapping; two-electron atom; V-type system
• ISSN: 1367-2630; 1367-2630
• DOI: 10.1088/1367-2630/17/3/033044

We observe coherent population trapping (CPT) in a two-electron atom-174Yb-using the transition. CPT is not possible for such a transition according to one-electron theory because the magnetic sublevels form a V-type system, but in a two-electron atom like Yb, the interaction of the electrons transforms the level structure into a Λ-type system, which allows the formation of a dark state and hence the observation of CPT. Since the two levels involved are degenerate, we use a magnetic field to lift the degeneracy. The single fluorescence dip then splits into five dips-the central unshifted one corresponds to coherent population oscillation, while the outer four are due to CPT. The linewidth of the CPT resonance is about 300 kHz and is limited by the natural linewidth of the excited state, which is to be expected because the excited state is involved in the formation of the dark state.