Photo Echo and Optical Nutation in Molecules

Photon echo and optical nutation have been easily observed in ${\mathrm{C}}^{13}$ ${\mathrm{H}}_3$F and N${\mathrm{H}}_2$D by applying Stark pulses which shift the molecular levels into resonance with cw laser radiation. Numerical computations of the nutation effect agree with observation, and echo characteristics closely follow predictions of existing theories. The $T_2^{}{}_{}{}^{\prime }$ pressure dependence, from infrared-echo measurements, indicates that ${\mathrm{C}}^{13}$ ${\mathrm{H}}_3$F relaxes primarily by rotational energy transfer.