Measurement of optical gain in CO gas excited only by fission fragments

Gain has been measured in high-density (∼ 0.5 amagat) CO gas, which was cooled to 77 K and excited with an intense burst of fission fragments induced by a fast-burst reactor (Sandia SPR II). Peak-gain coefficients
\lsim 0.5
percent/cm were measured in pure CO over the wavelength range
5.1-5.33 \mu
, for fission-fragment energy depositions ∼ 200 J/l. Interpreting the measured gains with an approximate steady-state vibrational distribution implies that
\sim 25-70
percent of the fission-fragment energy deposited in the CO is appearing as excitation of the vibrational modes of the CO molecule.