Rb vapour Zeeman optical spectroscopy in a self-calibrated magnetic field

Abstract High-resolution optical spectroscopy of Rb atoms in an intermediate-Zeeman magnetic field regime is performed. Magnetic fields between 0.05 T and 0.13 T are measured. We introduce a measurement approach based on three-level $$\Lambda $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mi>Λ</mml:mi> </mml:math> systems where the open-loop frequency energy separation is determined by the applied magnetic field. Using this method an accuracy better than 100 ppm is reached in a measurement series. In parallel, on the basis of complementary measurements based on three-level V systems we obtain the first experimental value of the Landé g-factor of the first excited state for $$^{85}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mmultiscripts> <mml:mrow/> <mml:mrow/> <mml:mn>85</mml:mn> </mml:mmultiscripts> </mml:math> Rb, $$^{85}g_J(5P_{1/2})$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mmultiscripts> <mml:mrow/> <mml:mrow/> <mml:mn>85</mml:mn> </mml:mmultiscripts> <mml:msub> <mml:mi>g</mml:mi> <mml:mi>J</mml:mi> </mml:msub> <mml:mrow> <mml:mo>(</mml:mo> <mml:mn>5</mml:mn> <mml:msub> <mml:mi>P</mml:mi> <mml:mrow> <mml:mn>1</mml:mn> <mml:mo>/</mml:mo> <mml:mn>2</mml:mn> </mml:mrow> </mml:msub> <mml:mo>)</mml:mo> </mml:mrow> </mml:mrow> </mml:math> =0.66709(7), and for $$^{87}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mmultiscripts> <mml:mrow/> <mml:mrow/> <mml:mn>87</mml:mn> </mml:mmultiscripts> </mml:math> Rb, $$^{87}g_J(5P_{1/2})$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mmultiscripts> <mml:mrow/> <mml:mrow/> <mml:mn>87</mml:mn> </mml:mmultiscripts> <mml:msub> <mml:mi>g</mml:mi> <mml:mi>J</mml:mi> </mml:msub> <mml:mrow> <mml:mo>(</mml:mo> <mml:mn>5</mml:mn> <mml:msub> <mml:mi>P</mml:mi> <mml:mrow> <mml:mn>1</mml:mn> <mml:mo>/</mml:mo> <mml:mn>2</mml:mn> </mml:mrow> </mml:msub> <mml:mo>)</mml:mo> </mml:mrow> </mml:mrow> </mml:math> =0.6663(2). Our approach is unprecedented in the literature for Rb. Graphic abstract Experimental results for the Land´e g-factor of the first excited state of Rb