Chemiluminescence of ethylene in an inert matrix and the probable infrared spectrum of methylene

Photolysis of diazomethane in solid matrices at 6 or 10 °K and its subsequent thermoluminescence have been reinvestigated. At 11-12 °K, the thermoluminescence consists of a broad emission at 5220±4 Å and a weak progression with spacing 338 cm^-1 in the 6000-7600 Å region, the latter probably due to an impurity. Above 15 °K, the spectrum is dominated by a broad emission (180 cm^-1 FWHM) centered at 5987 Å, the red glow detected earlier. The emitter responsible for the 5220 Å feature is not clear, though the frequency is close to that of the atomic K(²D→⁴S) transition. The 5987 Å emission is best assigned to the C₂H₄(Z or V→T) transition excited through the reaction of CH₂(³B₁) molecules either with CH₂ or CH₂NN. This C ₂H₄ transition has not previously been accessible to experiment. The infrared spectra of the photolysis products at 10 °K indicate that absorptions at 1115 cm^-1 (Ar) and 1109 cm^-1 (Xe) can be attributed to ν₂, the bending mode of CH₂ in its ground state. This assignment may be of significance in the interpretation of photoelectron detachment measurements of the CH₂ triplet-singlet splitting, tending to favor the 9 kcal/mole value.