A new visible emission system, tentatively assigned to the trichloride radical, has been observed in a solid Ar matrix. Cl 3 was prepared by photodissociation of HCl and permanent cage exit of the H atom from HCl/Cl 2 dimer trapping sites. Following photodissociation at 193 nm, laser excitation and wavelength-resolved fluorescence measurements were used to examine the photoproducts. Excitation at 308 nm produced a broad emission centered at 470 nm. This band was emitted with a lifetime of 44 ( 2 µs. An excitation spectrum, recorded by monitoring the 470 nm emission, exhibited a single broad peak centered at 312 nm. The emission spectrum and lifetime were in agreement with gas phase results that were previously attributed to Cl 3 [Kawasaki et al. J. Phys. Chem. 1989, 93, 7571]. The excitation spectrum correlates with the 320 nm absorption band of the isoelectronic F 2 Cl radical [Prochaska and Andrews, J. Inorg. Chem. 1977, 16, 339]. Additional elements of circumstantial evidence that support assignment of the matrix observations to Cl 3 are presented.