Single-laser two-step fluorescence detection of atomic hydrogen in flames

We describe a new single-laser, two-step fluorecence technique for detecting atomic hydrogen and demonstrate its application to flame measurements. This method provides the advantages of a previously demonstrated two-step method (two-photon 243-nm n = 1 ? n = 2 excitation and subsequent single-photon 656-nm n = 2 ? n = 3 excitation, by using two beams produced with two dye lasers) but with a much simpler experimental implementation (two-photon 243-nm n = 1 ? n = 2 excitation and subsequent single-photon 486-nm n = 2 ? 4 excitation, by using the fundamental and frequency-doubled beams from a single 486-nm dye laser).