Microwave Zeeman effect of methanol

Zeeman effect of the rotational spectrum of methanol has been measured in a magnetic field of 7.0 kG produced by rectangular bar magnets of neodymium. Thirty low J, K (J ≤ 10, K ≤ 3) rotational transitions, including those in the excited torsional states, were observed. Their Zeeman effect splittings were measured with uncertainties of about 5%, and the four diagonal elements of the rotational g tensor, including the effect of internal rotation of the methyl group, were determined. Using this g tensor, the g factors of low J, K levels can be calculated with an uncertainty of about 5%. They allow us to calculate Zeeman shifts of rotational transitions of methanol observed in interstellar space.