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Modeling of the Low‐Frequency Noise in Thermal Lens Spectrometry
Author(s) -
MartínBiosca Yolanda,
Rozé Claude,
RamisRamos Guillermo
Publication year - 1998
Publication title -
israel journal of chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.908
H-Index - 54
eISSN - 1869-5868
pISSN - 0021-2148
DOI - 10.1002/ijch.199800018
Subject(s) - chemistry , noise (video) , lens (geology) , signal (programming language) , thermal , transient (computer programming) , low frequency , natural frequency , harmonic , fundamental frequency , optics , mechanics , computational physics , acoustics , physics , vibration , thermodynamics , artificial intelligence , computer science , image (mathematics) , programming language , operating system , astronomy
The low‐frequency noise observed in thermal lens spectrometry (TLS) can be modeled by assuming that the heated region, constituted by the thermal lens gradient and associated convective stream, behaves as a weakly damped harmonic oscillator with a natural frequency, v o , which is forced to move at an externally imposed pump frequency, v p . Out‐of‐phase lower‐frequency oscillations of the TLS signal can be produced both by transient events, such as the beginning of the TLS experiment and small changes in the pump beam stability, and by drift of boundary conditions, such as the temperature of the surroundings. A model is developed and checked using 1‐(2‐pyridylazo)‐2‐napthol (PAN) solutions in silicone oil. Consequences of analytical interest are drawn; e.g., the signal‐to‐noise ratio of the TLS experiments is improved by pumping at the resonance frequency, where v p = v o .