The storable energy of a high-power laser is inversely proportional to its stimulated emission cross-section σ. By adding a foreign gas, the emission line is broadened and is thereby lowered. We have measured σ of the iodine laser as a function of the pressure of several gases (Ar, N2, CO, CO2, SF6, CF3Br, C3F7I, CF2Cl2, (CF3)2CO) by an absolute and a relative method. 1/σ is a linear function of the pressure in spite of the fact that overlapping of the hyperfine structure components varies considerably in the range investigated. For optimum energy storage, CO2 is a good compromise between pressure broadening and chemical deactivation of the excited I-atoms. At one atmosphere of CO2, 5 to 7 J/cm-2 can be stored, the hyperfine structure is largely blurred, and the amplification of pulses shorter than 100 psec should be possible