An improved CO2 laser intracavity photoacoustic spectrometer for trace gas analysis

Abstract

This work describes an improved CO2 laser intracavity photoacoustic spectrometer. It can detect and measure small quantities of trace gases in air. The measured absorption sensitivity of 3.3×10−10 cm−1 corresponds to a mixture of 11 pptv (volume parts per trillion) of ethene in nitrogen. The sensitivity and reliability of the instrument were enhanced by reducing the level of background signals originating from optical and acoustical sources. The sensitivity reached is comparable with the best existing continuous measuring instruments while the background signal is two orders of magnitude smaller. The improvements are described in detail and a comparison to previous work is made. A first measurement demonstrates the suitability of the apparatus for biological applications.

Ultrasensitive CO2 laser photoacoustic system

“…From this table it clearly results that the best sensitivity is obtained in our extracavity PA instrument, where a min (cm À1 ) is better by one or two orders of magnitude than with intracavity arrangements. The minimum detectable concentration obtained by us is four times lower than that obtained by Harren et al [12] and 50 times lower than that reported by Fink et al [17].…”

“…Most published papers give values between 37 and 200 V cm/W [10,12,[15][16][17] and only few reports obtained similar values [2,14] or a higher value [13] (by using a microphone with a very large responsivity).…”

Cellulysin from the plant parasitic fungus Trichoderma viride elicits volatile biosynthesis in higher plants via the octadecanoid signalling cascade

“…In order to test whether or not the previously reported xylanase‐induced (minor component of crude cellulysin) ethylene biosynthesis [30, 31]in leaf tissue of N. plumbaginifolia can be also provoked in P. lunatus , the gas phase of cellulysin‐treated leaves was analysed by photoacoustic spectroscopy (PAS) [32]. The method is highly sensitive for several low molecular compounds (detection limit for ethylene: 0.03 μg m −3 ) and allows a continuous monitoring of the gas phase.…”

“…The ethylene production was measured with a photoacoustic laser spectrometer consisting of a line‐tunable infrared CO 2 ‐laser and a resonant photoacoustic cell [32, 33]. The background free detection method allows the detection of ethylene at concentrations at a pptv (volume parts per trillion) level.…”

Eine „Atemgasanalyse”︁ für Pflanzen: Der photoakustische Spurengasnachweis in der Pflanzenphysiologie

“…Die dortigen Erfahrungen waren eine wesentliche Anregung für den Aufbau eines Labors in unserer Arbeitsgruppe [6]. Das Blockschaltbild eines solchen Messplatzes ist in Abb.…”