CH3I low-n Rydberg states in supercritical atomic fluids near the critical point

Vacuum ultraviolet photoabsorption spectra of CH3I 6s and 6s' Rydberg states doped into supercritical argon, krypton, and xenon perturbers were measured from low density to the density of the triple point liquid at noncritical temperatures and on an isotherm near the perturber critical temperature. A full line shape analysis of these spectra was performed using a single set of intermolecular potential parameters for each dopant/perturber system. The resulting perturber induced shift of the simulated adiabatic transition of the 6s and 6s' Rydberg states is presented as a function of perturber number density, and this shift illustrates a perturber critical point effect on the excitation energies of the molecular low-n Rydberg states. (C) 2009 Elsevier B.V. All rights reserved.