# Spectroscopic Lineshapes

### Introduction

natural broadening, collisional broadening, power broadening, and Doppler broadening. Natural, collisional, and power broadening are homogeneous mechanisms and produce Lorentzian lineshapes, and Doppler broadening is a form of inhomogeneous broadening and has a Gaussian lineshape. The general form of Lorentzian and Gaussian lineshapes are shown below. Combinations of Lorentzian and Gaussian lineshapes can be approximated by a Voigt profile.
*Lorentzian (red) and Gaussian (blue) lineshapes normalized to equal maximum*

Collisions broaden spectroscopic linewidths by shortening the lifetime of the excited states.

Power broadening occurs by shortening the lifetime of the excited state due to stimulated emission.

Doppler broadening is due to the distribution of atomic velocities (speed and direction), which each have a Doppler shift with respect to an observer.

### Further Information

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Copyright © 1996 by Brian M. Tissue

updated 2/25/96