Emission spectra (in the region 100-200 nm) of the excimers Ar-2* Kr-2*, and Xe-2* produced in a dc jet discharge with supersonic expansion were used to determine vibrational temperatures of the excimers, and to analyze the process of excimer relaxation from high vibrational levels near dissociation of the A (3) Sigma(u)(+)(1(u)) states to the lowest levels. The observed narrow bandwidths of the second continua yielded population distributions with at least 80% in the upsilon=0 levels at thermal equilibrium, for all three gases, corresponding to vibrational temperatures of 280, 95, and 82 K for Ar-2+, Kr-2* and Xe-2* respectively. Changes in relative intensities of the first and second continua with pressure were monitored by optical pumping of atoms in the 1s(5) metastable level [precursor of the excimer A (3) Sigma(u)(+)(1(u)) stale], and the resulting difference spectra were analyzed in terms of vibrational relaxation to the upsilon similar to 0 levels. A simple model based on collisional relaxation was developed to calculate the VUV band spectra. Comparisons of the Ar-2* spectra with the model showed that vibrational relaxation accounted for the observed difference spectra, up to plenum pressures of similar to 7 atm. Departures from this model at higher pressures for Ar-2*, and particularly the observed behavior of Kr-2* and Xe-2* difference spectra, indicated that populations in the lowest vibrational levels were affected by additional processes, and not only by vibrational relaxation of excimers formed by association.