The ultrafast optical Kerr effect in liquid fluoroform: an estimate of the collision-induced contribution

Abstract

The ultrafast optical Kerr effect (OKE) of liquid fluoroform at 296 K and 125 bar has been measured with 25 fs pulses. Results are compared to those of chloroform which is structurally similar. The nuclear response in fluoroform is ca. 110 times weaker than in chloroform. Diffusive relaxation of the anisotropy with 0.80±0.10 ps time constant is assigned to rotational motion. The OKE spectral density is compared to the far-infrared spectra of liquid fluoroform with a power law which relates the corresponding relaxation functions. It follows that collision-induced effects account for 25–30% of the OKE spectral integral.