Angular and internal state distributions of H2+ generated by (2+1) resonance enhanced multiphoton ionization of H2 using time-of-flight mass spectrometry

We report direct measurement of the anisotropy parameter beta for the angular distribution of the photoelectron and photoion in (2 + 1) resonance enhanced multiphoton ionization process of H-2 X (1)Sigma(+)(g) (v = 0, J = 0) molecules through the intermediate H-2 E,F (1)Sigma(+)(g) (v' = 0, J' = 0) level (lambda = 201.684 nm) using a time-of-flight mass spectrometer. The time-of-flight spectra were recorded as the direction of polarization of the ionizing laser was varied with respect to the flight axis of the H-2 molecular beam and were fitted to an angular distribution in an appropriately rotated coordinate system with the z-axis oriented along the time-of-flight axis. The anisotropy parameter beta was found to be 1.72 +/- 0.13 by fitting the time-of-flight spectra and agreed with previous measurements. Using secondary ionization with a delayed laser pulse of different wavelength, we also determined the vibrational energy distribution of the ions, showing that 98% +/- 4% of the ions are generated in their ground vibrational state, in agreement with the calculated Franck-Condon factors between the H-2 E,F (1)Sigma(+)(g) (v' = 0) and H-2(+) X (1)Sigma(+)(g) (v '') vibrational levels. Published by AIP Publishing.