Optical zeeman spectroscopy of the (0, 0) A ²Π-X ²Σ⁺ band system of magnesium hydride

The Zeeman effect on lines in the (0, 0) A ²Π-X ²Σ⁺ band system of a cold molecular beam sample of magnesium hydride, MgH, has been recorded at high resolution (FWHM ≅60 MHz) and analyzed. The lines associated with the lowest rotational levels are detected for the first time. The field-free spectrum was analyzed to produce spectroscopic parameters for the A ²Π (v = 0) state. The experimentally observed magnetic tuning of the low-rotational spectral features at field strengths comparable to those found in sunspots is accurately modeled by assuming that the electronic spin and orbital magnetic g-factors, g _S and g_L, of the A ²Π and X ²Σ⁺ states are 2.002 and 1.000, respectively, and g_l is-0.0023 for the X ²Σ⁺.