Quadrupole Coupling in the Hyperfine Structure of the Spectrum of La I

The hyperfine structure of the level 5 s 5 p 5 3 P 2 was studied, and the quadrupole moment Q '(I 137 ) withont shielding correction was deduced to be -0.49±0.08 barn, whereas the value of Q ' deduced from 5 p 5 2 P 3/2 and 6 s 4 P 5/2 and 7 p 4 D 7/2 of I I is -0.66 barn, the most probable value of Q being -0.62 barn. This discrepancy seems to show that the shielding correction for the configuration 5 s 5 p 5 of I II is positive. The interval factor of the level 5 s 5 p 5 1 P 1 was found to be too large to give proper interpretation.