Calculation and measurement of high-order harmonic energy yields in helium

We present calculations of the energy yields of high-order harmonic radiation produced by 526-nm laser light focused into a helium gas jet. The intensity-dependent dipole moments of helium calculated by numerical integration of the Schrödinger equation have been used in a numerical solution of the wave equation to determine the energy yields of harmonics in the 30–17-nm wavelength range. These calculations are compared with measured absolute energy yields and are shown to be in good agreement with experiment.