Photoacoustic trace detection of gases at the parts-per-quadrillion level with a moving optical grating [Applied Physical Sciences]
The amplitude of the photoacoustic effect for an optical source moving at the sound speed in a one-dimensional geometry increases
linearly in time without bound in the linear acoustic regime. Here, use of this principle is described for trace detection
of gases, using two frequency-shifted beams from a CO2 laser directed at an angle to each other to give optical fringes that move at the sound speed in a cavity with a longitudinal
resonance. The photoacoustic signal is detected with a high-
Q, piezoelectric crystal with a resonance on the order of
443 kHz. The photoacoustic cell has a design analogous to a hemispherical laser resonator and can be adjusted to have a longitudinal
resonance to match that of the detector crystal. The grating frequency, the length of the resonator, and the crystal must
all have matched frequencies; thus, three resonances are used to advantage to produce sensitivity that extends to the parts-per-quadrillion
Keeping up-to-date with research can feel impossible, with papers being published faster than you'll ever be able to read them. That's where Researcher comes in: we're simplifying discovery and making important discussions happen. With over 19,000 sources, including peer-reviewed journals, preprints, blogs, universities, podcasts and Live events across 10 research areas, you'll never miss what's important to you. It's like social media, but better. Oh, and we should mention - it's free.
Researcher displays publicly available abstracts and doesn’t host any full article content. If the content is open access, we will direct clicks from the abstracts to the publisher website and display the PDF copy on our platform. Clicks to view the full text will be directed to the publisher website, where only users with subscriptions or access through their institution are able to view the full article.