Briefly, the ions are formed in an atmospherically-isolated ESI source, where they are then guided through a series of ion guides to a cryogenically cooled octopole ion trap. Inside the cryogenically cooled trap (cooled by Sumitomo RDK-408D2 cold head), the ions are collisionally cooled via introduction of pulsed helium gas. Most spectra of the clusters discussed herein were recorded via cryogenic ion vibrational predissociation (CIVP), where an inert tag species, in this case N 2 gas, is seeded into the cryogenic ion trap. The trap is cooled down to approximately 45 K in order for the tag to physisorb onto the cluster of interest. The tagged ion packet is then accelerated down a field free flight tube to the laser crossing, where a portion of the ion packet is intersected by tunable infrared laser light produced by a Nd:YAG-pumped OPO/OPA system (LaserVision). As the laser scans, the tagged cluster will absorb a single photon when resonant with an IR transition, resulting in the tag desorbing from the cluster. A reflectron then separates the ions that lose a tag from those that did not, before they reach the microchannel plate detector. Spectra are computed from the ratio of untagged ions to tagged plus untagged ions multiplied by laser power, as a function of wavelength. CIVP allows for the collection of a linear spectrum and therefore direct comparisons of relative peak intensities can be made.