The 5P3/2 → 6PJ (J=1/2,3/2) Electric Dipole Forbidden Transitions in Rubidium

This paper presents a general review of the results of the experimental and theoretical work carried out by our research group to study the <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mn>5</mn><msub><mi>P</mi><mrow><mn>3</mn><mo>/</mo><mn>2</mn></mrow></msub><mo stretchy="false">→</mo><mn>6</mn><msub><mi>P</mi><mi>J</mi></msub></mrow>emantics></math></inline-formula> electric quadrupole transition in atomic rubidium. The experiments were carried out with room-temperature atoms in an absorption cell. A steady-state population of atoms in the <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mn>5</mn><msub><mi>P</mi><mrow><mn>3</mn><mo>/</mo><mn>2</mn></mrow></msub></mrow>emantics></math></inline-formula> excited state is produced by a a narrow-bandwidth preparation laser locked to the D2 transition. A second CW laser is used to produce the forbidden transition with resolution of the <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mn>6</mn><msub><mi>P</mi><mi>J</mi></msub></mrow>emantics></math></inline-formula> hyperfine states of both rubidium isotopes. The process is detected by recording the 420(422) nm fluorescence that occurs when the atoms in the <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mn>6</mn><msub><mi>P</mi><mi>J</mi></msub></mrow>emantics></math></inline-formula> state decay directly into the <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mn>5</mn><mi>S</mi></mrow>emantics></math></inline-formula> ground state. The fluorescence spectra show a strong dependence on the relative polarization directions of the preparation laser and the beam producing the forbidden transition. This dependence is directly related to a strong anisotropy in the populations of the <inline-formula>