THz Zeeman spectrum of NO molecule encapsulated in the fullerene molecular cage.

NO molecule has electron spin ½ and orbital angular momentum 1. The effective g-factor of the electronic ²Π_1/2 ground state is less than 10^-2. However, the first electronic excited state ²Π_3/2 which is 123cm^-1 higher, has the effective g-factor of the order of one [1]. The magnetic field induced Zeeman splitting of both states has been studied in the gas phase [2,3]. Here we study the Zeeman splitting of NO ²Π_3/2 state at temperature 2.5 K, not possible in the gas phase, by encapsulating NO molecule in the molecular cage of C₆₀. The spectral line at 121.7cm^-1 in the THz absorption spectrum splits into four components. We followed the splitting in magnetic field up to B=17 T. The B-dependent spectra were fitted by taking into account orbital angular momentum coupling to the molecule axis, spin-orbital interaction and electron spin and orbital moment coupling to the magnetic field.

[1] G. M. Mizushima et al, Phys. Rev. A5, 143 (1972), ibidem p. 2276.

[2] W.L. Meerts, L. Veseth, J. Mol. Spectrosc. 82, 202 (1980)

[3] K. Hakuta, H. Uehara, J. Mol. Spectrosc. 58, 316 (1975)