Direct absorption measurement of the spin–orbit splitting and 2 P 1/2 radiative lifetime in atomic fluorine (2 p 5)

We report the first direct measurement of the fluorine atom ground state fine structure transition. The transition was measured by diode laser absorption spectroscopy. The position of the (J=3/2, F=2)→(J=1/2, F=1) absorption line was measured with high precision relative to a pure rotational transition in H2O, establishing the fine structure energy splitting as 404.082 cm−1 ±0.025. The measured transition probability for the hyperfine component is 1.26×10−3 s−1 (±25%), yielding a radiative lifetime of 660 s for the 2P1/2 fine structure level.