We have demonstrated previously that one can read and write information in a diatomic molecule as the population distribution which referred to as a 'population code' (Hosaka et al., 2010 [16]; Ohmori et al., 2006 [9]; Katsuki et al., 2007 [10]). As a next step to this read and write process, modification of the population code is necessary to develop logic gates. Here we demonstrate that the population code in the iodine molecule can be modified by near-infrared femtosecond laser pulses. (C) 2010 Elsevier B. V. All rights reserved.