The ArF laser-induced photoisomerization of FC.tplbond.CF (2) to F2C:C: (1) was obsd. by measuring the IR difference spectrum in an Ar matrix at 10 K and comparing with ab initio vibrational frequencies. Fermi resonance between n4 and n2 + n5 in 1 was obsd. and discussed. The UV absorption of 1 was also assigned. Photogeneration of 1 in a matrix doped with 1% CO or 1% N2, followed by annealing to 35-42 K, led to synchronous depletion of 1 and growth of F2C:C:X (X = CO, N2, resp.). [on SciFinder (R)]