COMPARISON OF VARIOUS 2-PHOTON EXCITATION SCHEMES FOR LASER-INDUCED FLUORESCENCE SPECTROSCOPY IN ATOMIC-HYDROGEN

Various two-photon excitation schemes for laser-induced-fluorescence s pectroscopy in atomic hydrogen have been experimentally investigated. The results are compared with one another and with theoretical predict ions. A tunable narrow-bandwidth ArF excimer laser (oscillator-amplifi er system) in combination with a Raman cell was used as the light sour ce. Atomic hydrogen at room temperature and at densities of approximat ely 10(14) cm-3 was provided by a flow-tube reactor. Excitation was fr om the ground state to the excited n = 3 and n = 4 states, and fluores cence light was observed at Balmer-alpha and -beta wavelengths, respec tively. Various wavelength combinations [(205 nm x 2) and (193 + 219 n m) for excitation to n = 3 and (193 + 195 nm) for excitation to n = 4] , polarizations (linear, circular, and unpolarized), and bandwidths (1 10, 11, and 0.8 cm-1) were used for the excitation process.