Density measurements of Hg(63P0,1,2) in a discharge using saturated laser absorption and hook methods

Two laser-based techniques are used to derive radial density distributions and absolute densities for the three 63PJ excited states of mercury in the positive column of a low-pressure Hg-Ar dc discharge. In the saturated laser absorption (SLA) method, a pulsed dye laser, traversing the discharge axially, is scanned through one of the 63PJ→73S1 transitions. At high laser powers the power absorbed from the beam on resonance approaches a constant saturated value directly proportional to the number density of Hg atoms in the 63PJ state selected. On-axis absolute density estimates and radial distribution results are presented for the three states at several discharge conditions. The hook method, a well-known interferometric technique, more accurately establishes the absolute densities on axis, and several off-axis measurements are compared with SLA results.