The laser action of an all-gas-phase iodine laser that uses molecular iodine as a source of iodine atoms has been demonstrated. The laser is based on the energy transfer reaction between metastable NCl(a(1)Delta) and ground-state I(P-2(3/2)) atoms. The replacement of iodine source from HI to I-2 had been desired, but it was considered to be difficult due to the high deactivation reaction rate of excited iodine atoms by residual I-2. In this system, iodine atoms are produced by microwave discharge. Continuous-wave laser output of 35 mW with a duty factor of 40% was observed. This is 70% of the output from the same system with HI iodine source. (C) 2010 Published by Elsevier B.V.