Observation of Doppler-free two-photon absorption in the ν3 bands of CH3F

Abstract

We report the first observation of Doppler-free two-photon absorption in a molecule using two fixed-frequency infrared optical fields in combination with molecular Stark tuning. The coincidences of the P14 and P30 lines of two oppositely directed cw CO2 lasers at 9.4 μm with the R(1, 1)0→ν3 and R(2, 1)ν3→2ν3 lines of C12H3F are used to measure the pressure-broadening coefficient (Δνp=41.3±1.0 MHz/Torr) and pressure shift (Δνs=2.1±0.1 MHz/Torr) of the 0→2ν3 transition. © 1975 The American Physical Society.