The original purpose of this study was to address a partition of propulsive energy between air and metal, when the breakdown is initiated at the metal surface and/or in adjacent air space. Coupling coefficient as a function of air pressure varied in the range 4 mTorr – 1 atm is presented. The experiments were conducted by focusing output pulses of a TEA CO2laser system (0.2‐&mgr;s pulsewidth at 10.6 &mgr;m wavelength and ∼ 10.0 J energy) on aluminum targets. Coupling coefficients were derived from the pendulum displacements. © 2004 American Institute of Physics