The effect of O2 on the number and IR intensity of lasing lines has been quantitatively studied for a pulsed F2/H2 laser. The sequence of appearance of each individual line in the lasing process is found to be quite regular with positive J-shift. Rotational nonequilibrium behavior is exibited on all v = 1~6 levels. The cascade effect is markedly shown for transition P6 (4) - P1 (9) and P6(6) -P1(11). These experiments are in good agreement with the predictions of our computer modeling.