When testing Bohr's theory by Franck-Hertz experiment, we have electrons colliding with Hg atoms. a Hg atom will absorb electron's energy when this energy can make it jumping to a higher energy level. I wonder Hg is more like L-S coupling or j-j coupling, for I want to measure its higher excited state by accelerating electrons faster. By the way, I have known that L-S coupling is effected when residual electrostatic is far lager than spin-orbit interaction. Thank you!