Infrared photodissociation spectra of isomeric SiOH+–Arn (n=1–10) complexes Original Research Article

Infrared photodissociation spectra of mass-selected SiOH+–Arn complexes (n=1–10) have been recorded in the vicinity of the OH stretch (ν1) vibration of SiOH+. The SiOH+–Ar dimer has also been investigated by ab initio calculations at the MP2 level and two stable isomers have been found. The linear proton-bound global minimum (De=1117 cm−1) and the less stable T-shaped silicon-bound geometry (De=938 cm−1) are separated by an isomerization barrier of ∼500 cm−1. Three rotationally resolved bands observed in the dimer spectrum are assigned to the ν1 fundamental (3444.9 cm−1) and the ν1+νs (3554.6 cm−1) and ν1+2νb (3581.5 cm−1) combination bands of the linear isomer, whereas a weak unresolved band centered at 3673 cm−1 is attributed to the ν1 fundamental of the T-shaped isomer. The assignments are based on the rotational analysis, vibrational frequencies and comparison with the ab initio results. Systematic ν1 vibrational band shifts observed in the spectra of larger clusters have allowed to monitor the cluster growth and identify coexisting isomers.