Laser measurement of the photodetachment cross section of H- at the wavelength 1064 nm

A method is described to measure photoexcitation cross sections, relying on the expected behavior of the signal in the saturated regime, when excitation is provided by a Gaussian light beam. The method is implemented on a negative ion beam, with a single-mode pulsed Nd:YAG laser, to make a laser measurement of the photodetachment cross section of H-, at the wavelength 1064 nm. This cross section is of importance both as a photodetachment cross section of the most elementary negative ion and as a key parameter for the production of fast neutral H-0 or D-0 atoms, by photodetachment of accelerated anions. The obtained value 4.5(6) x 10(-21) m(2) is greater than the one known from older measurements and most ab initio calculations.