Novel method for measuring Dicke narrowing by wavelength modulation spectroscopy

Summary form only given. Wavelength modulation spectroscopy signals exhibit features of frequency derivatives of the lineshape profile. Detection at the modulation frequency, f, yields signals that approximate the first derivative, and detection at the frequency Nf yields a signal that approximates the N/sup th/ derivative. Second harmonic (2f) detection has been used frequently in the past, while we have recently demonstrated several advantages of higher harmonic detection. These include an increased sensitivity to density fluctuations, and an increased resolution of overlapping lines.