Wavelength, linewidth, and intensity measurements have been made from 3000 to 4500 Å of the spectra of triatomic carbon molecules trapped in solid matrices of Ar, Kr, Xe, O2, N2, CO2, and SF6 at 4° and 20°K. The carbon source was a Knudsen cell, operated at temperatures up to 2900°K, from which effused a molecular beam with known densities of C3. Absorption transitions are assigned to vibrational levels of both upper and lower states of the 1Πu—X 1Σg+ 4050-Å group of C3. The fundamental vibrational frequencies ν1 and ν2 for the upper 1Πu state, ν2 for the ground 1Σg+ state, and Renner constants for ν2 of the 1Πu state in these matrices are given. Measurements of absorption intensities give an oscillator strength, averaged for all matrices, equal to 6×10−2 for the C3 group. Little or no matrix effect on the intensities is found. However, experimentally determined corrections to the intensities are necessary for effects caused by apparent diffusion of carbon in the matrices to form nonabsorbing carbon aggregates. C3 linewidths vary with matrix from 40 to 500 cm−1, and C3 line shifts vary from −410 to 1065 cm−1. All matrix shifts are to the red except in the case of the CO2 matrix. No definite effect of temperature on linewidths or shifts is found.

Barger, R. L., & Broida, H. P. (1965). Spectra of C3 in Solidified Gases at 4° and 20°K. The Journal of Chemical Physics, 43(7), 2364–2370.