Pump-induced population changes in broadband coherent anti-Stokes Raman scattering.

Using a powerful, excimer-laser-pumped broadband coherent anti-Stokes Raman scattering (CARS) system, we have observed considerable changes in the populations of room-temperature nitrogen under atmospheric pressure. Pump-induced populations in the first, second, and third vibronic bands of N2 at room temperature resulted in an apparent vibrational temperature of 2550 K. The implications for broadband N2 CARS thermometry are discussed.