Determination of photofragment ion translational energy and angular distributions in an octopole ion guide:: A case study of the Ar2+ and (N2O•H2O)+ cluster ions

The first measurement of ion photodissociation product recoil velocity and angular anisotropy in an octopole ion guide are presented. The experimental and numerical procedures required to obtain photofragment ion translational energy and angular distributions are discussed. Cluster ions are photodissociated in an octopole ion guide, and photofragment ion velocity distributions are measured using time-of-flight (TOF). The instrumental discrimination function is determined using guiding held variation (VAR). A validation study using the (2)Sigma(g)(+)<--(2)Sigma(u)(+) transition of Ar-2(+) probed at 300 nm and a photodissociation dynamics study of (N2O . H2O)(+) to form N2OH++OH, N2O++H2O, and H2O++N2O in the 458-657 nm range are presented. The H2O+ and N2O+ photofragment translational energy and angular distributions are derived, and new information regarding the photodissociation of the (N2O . H2O)(+) cluster ion is obtained. (C) 1998 American Institute of Physics. [S0021-9606(98)00541-8].