Density measurements in air by optically exciting the Cordes bands of I2

We describe an optical method based on laser-induced fluorescence for obtaining instantaneous measurements of density along a line in low-density air seeded with I2 . The Cordes bands of I2 (D 1 u + X 1 g + ) are excited with a tunable ArF excimer laser. Air densities in the range (0.1 - 6.5) ? 1017 cm-3 are measured over 295 - 583 K using the density-dependent emission ratio of two emission bands of I2 ; the 340 nm bands and the diffuse-structured McLennan bands near 320 nm.