Theoretical investigation of the temperature dependence of the 2f-wavelength modulated diode-laser absorption signal

The temperature dependence of 2f-wavelength modulated signals has been inve stigated theoretically both for single-transition atoms (representing mono- isotopic atoms lacking hyperfine structure) and the 780 nm 12-peak transiti on in Rb using a previously developed simulation methodology. The temperatu re dependence, denoted xi, is defined as the ratio of the relative change o f the 2f-signal (Delta (S) over bar(2f)/(S) over bar(2f)) to that of the te mperature (Delta T/T). For small modulation amplitudes, the temperature dep endence is plus and minus unity (xi(0)(L) = 1, xi(0)(G) = -1) on resonance of single-transition atoms having Lorentzian and Gaussian broadened transit ions and slightly below unity (0.6 < xi(0)(V) < 0.8) for transitions with a Voigt profile under conditions prevailing in a graphite furnace. When opti mum modulation amplitudes are used the temperature dependence is smaller (\ xi\ < 0.1) as long as the sample has a low Sample Optical Thickness (SOT), however increasing with increasing SOT (e.g. xi(0)(V) > 1 for SOTs > 8 for a single Voigt broadened transition and xi(0)(Rb) > 1 for SOTs > 12 for the 780 nm transition in Rb). For detuned conditions, xi can take both larger and smaller values. (C) 1998 Elsevier Science B.V. All rights reserved.