Abstract
An exceptional property of photo-acoustic spectroscopy is the zero-background in wavelength modulation configuration while the signal varies linearly as a function of absorbed laser power. Here, we make use of this property by combining a highly sensitive cantilever-enhanced photo-acoustic detector, a particularly stable high-power narrow-linewidth mid-infrared continuous-wave optical parametric oscillator, and a strong absorption cross-section of hydrogen fluoride to demonstrate the ability of cantilever-enhanced photo-acoustic spectroscopy to reach sub-parts-per-trillion level sensitivity in trace gas detection. The high stability of the experimental setup allows long averaging times. A noise equivalent concentration of 650 parts-per-quadrillion is reached in 32 minutes.
Highlights
In molecular trace gas analysis, researchers are constantly pushing towards more sensitive, affordable and robust instruments as required by the industry and the scientific community
The strongest absorption lines of hydrogen fluoride (HF) are located around 2476 nm, which we are able to access with the special high-power narrow-linewidth optical parametric oscillator that produces coherent light at three principle wavelengths: a 1064 nm pump beam, a 1866 nm signal beam and a 2476 nm idler beam
The results presented in this article demonstrate a great potential of photo-acoustic spectroscopy, and especially cantilever-enhanced photo-acoustic spectroscopy (CEPAS), for remarkably sensitive and selective trace gas analyzers
Summary
In molecular trace gas analysis, researchers are constantly pushing towards more sensitive, affordable and robust instruments as required by the industry and the scientific community. Where Sm is the microphone sensitivity in mV/Pa, P is the optical power of the incident light in W, Ccell is the PA cell response constant in Pa/cm−1W, Ntot is the total number density of molecules in molecule/cm[3], cm is the concentration given as volume mixing ratio, and σ is the absorption cross section in cm−1 cm3/molecule It is self-evident that in order to measure the smallest concentration cm, one needs to maximize the other terms in the equation. We demonstrate the ability of CEPAS to reach a sub-ppt level sensitivity in trace gas detection, by making use of the linear scalability of the photo-acoustic signal by absorbed optical power. The highest HF sensitivity using laser absorption spectroscopy has been achieved in the work by Craig et al.[11] where they report a NEC of 38 ppt in 1 s, whereas in our experiment a NEC of 5 ppt is achieved in 1 s
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
