Inelastic Collision Induced by Intense Optical Radiation

A large cross section for inelastic collision is induced by an incident laser tuned to the frequency of the interatomic energy defect. We study energy transfer from the Sr $5p{}_{}{}^1{}_{}{}^{}P_{}^{\circ }{}_{}{}^{}$ level to the Ca $4d{}_{}{}^1{}_{}{}^{}D$ level and measure a cross section for inelastic collision of 3×${10}^{-16\mathrm{}}$ ${\mathrm{cm}}^2$ at a laser power density of 8.6×${10}^6$ W/${\mathrm{cm}}^2$ and a wavelength of 6409.0 Å.