Studies of the Kerr Effect in High Resolution Spectroscopy

Abstract

The general theory of the Kerr effect in the region of absorption bands is described. Expressions are derived for the Kerr constants B[=(nz − nx)ω/2πcFz2] and B′[=(kz − kx)ω/2πcFz2] for symmetric top molecules at frequencies close to transitions involving levels with K ≠ 0. The application of the theory to asymmetric top molecules and the inclusion of second-order effects are discussed.Kerr spectra of the 3390 Å band of formaldehyde and of the 3821 Å band of propynal have been photographed under high resolution. The most prominent lines in these spectra are those which show predominantly first-order Stark effects. Photoelectric methods are described involving (a) a rotating quarter-wave plate and (b) a rotating polarizer; they permit the recording of the pure birefringence (B) and pure dichroism (B′) respectively.