A calorimetric experiment, which combines picosecond C${\mathrm{O}}_2$-laser pulses with acoustic detection techniques, proves that the collisionless multiphoton dissociation of S${\mathrm{F}}_6$ is a statistical thermodynamic process. The standard Rice-Ramsberger-Kassel-Marcus theory of unimolecular reactions provides a quantitative explanation of the dissociation effect. The reaction rate is primarily limited by transitions in the quasicontinuum rather than by the anharmonicity of the first few discrete levels.

• Received 22 February 1977

DOI:https://doi.org/10.1103/PhysRevLett.38.1131