Isolated Line Shape Theory

This chapter is devoted to line-shape theories of an isolated transition. It provides some approximations needed to derive the formulations of isolated line shapes. The Doppler broadening is related to the thermal motion of the radiators and thus depends on the temperature of the considered medium. Various phenomenological line-shape models have been developed to account for non-Voigt effects, including Dicke narrowing and the speed dependences of collisional broadening and shift. The chapter focuses on these non-Voigt effects and provides a review of the most commonly used models that incorporate these refined collisional effects. The Hartmann–Tran profile has been widely adopted for the analysis of laboratory spectra, and its associated parameters are increasingly being incorporated into spectroscopic databases. Ongoing progress in experimental techniques for line-shape measurements is expected to drive the development of increasingly sophisticated phenomenological models, capable of fitting data within experimental uncertainties and noise levels.