The 304 nm photodissociation of the C-H symmetric stretch excited CH3I[v1=1,v2=0](v1 denotes the C-H symmetric stretch mode,and v2 denotes the umbrella mode)is studied with our simple photofragment translational spectrometer.An IR laser is used to excite the ground state CH3I[0,0]to the C-H symmetric stretch excited CH3I[1,0].With IR laser OFF and ON,the fractions of photofragments CH3(ν1,ν2)from the 304 nm photodissociation of CH3I[1,0]have been determined through the photofragment translational spectra(PTS)from measuring I and I*and also through the PTS from measuring CH3(0,0)(1,0)(0,1)and(1,1).The experimental results show that the C-H symmetric stretch vibration(v1=1)in parent molecules is about 66%retained in the photofragments in the I channel,but only 24%in the I*channel.The populations of photofragments CH3(0,2)and(0,3)are higher than CH3(0,0)and(0,1),showing strong inverted population both in I and I*channels. The 304 nm photodissociation of the CH symmetric stretch excited CH3I [v1 = 1, v2 = 0] (v1 denotes the CH symmetric stretch mode, and v2 denotes the umbrella mode) is studied with a simple photofragment translational spectrometer. An IR IR laser is used to excite the ground state CH3I [0,0] to the CH symmetrical stretch excited CH3I [1,0] .With IR laser OFF and ON, the fractions of photofragments CH3 (ν1, ν2) from the 304 nm photodissociation of CH3I [1 , 0] have been determined through the photofragment translational spectra (PTS) from measuring I and I * and also through the PTS from measuring CH3 (0,0) (1,0) (0,1) and (1,1). The experimental results show that CH symmetrical stretch vibration (v1 = 1) in parent molecules is about 66% retained in the photofragments in the I channel, but only 24% in the I * channel. The populations of photofragments CH3 (0,2 ) and (0,3) are higher than CH3 (0,0) and (0,1), showing strong inverted population both in I and I * channels.