The phase character of Zeeman modulation magnetic rotation laser spectroscopy

Zeeman modulation-magnetic rotation spectroscopic (ZM-MRS) technique is provided with not only high sensitivity and high signal-to-noise ratio, but also apparent phase character for studying molecular spectrum. It is quite helpful for assigning some complex molecular rotational spectra. As an example, the ZM-MRS spectra of NO₂ molecule was measured in the region between 16838cm^-1 and 16860cm^-1 with high resolution. The semi-classical magnetic rotation theory was used to explain the spectral feature and its phase relation with transition quantum number. It is in agreement with the experimental results. Finally, by using matrix diagonalization of effective Hamiltonian, the ZM-MRS spectra of NO₂ molecule were analyzed and a reasonable assignment was obtained.