The $3p^{ 4}$ $^{ 3}$P$_{ J}$ - $3p^{ 3}4p$ $^{ 3}$P$_{ J}$ transition in the sulphur atom is investigated in a precision two-photon excitation scheme under Doppler-free and collision-free circumstances yielding an absolute accuracy of 0.0009 cm$^{ -1}$, using a narrowband pulsed laser. This verifies and improves the level separations between amply studied odd parity levels with even parity levels in S I. An improved value for the $^{ 3}$P$_{ 2}$ - $^{ 3}$P$_{ 1}$ ground state fine structure splitting is determined at $396.0564$ (7) cm$^{ -1}$. A $^{ 34}$S - $^{ 32}$S atomic isotope shift was measured from combining time-of-flight mass spectrometry with laser spectroscopy.
Categories: physics.atom-ph