2023/02/01 by Jente R. Wubs, Uwe Macherius, Klaus‐Dieter Weltmann +6 · 1 voice · 2 citations
Chemistry · Engineering · Physics and Astronomy · #Advanced Chemical Physics Studies #Spectroscopy and Laser Applications #Terahertz technology and applications
paper · pdf · doi:10.1088/1361-6595/acb815
openalex publication_date 2023/02/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/29
Abstract This paper describes the first implementation of terahertz (THz) quantum cascade lasers for high-resolution absorption spectroscopy on plasmas. Absolute densities of ground state atomic oxygen were directly obtained by using the fine structure transition at approximately 4.75 THz. Measurements were performed on a low-pressure capacitively coupled radio frequency oxygen discharge. The detection limit in this arrangement was found to be <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mn>2</mml:mn> <mml:mo>×</mml:mo> <mml:msup> <mml:mn>10</mml:mn> <mml:mrow> <mml:mn>13</mml:mn> </mml:mrow> </mml:msup> </mml:math> cm −3 , while the measurement accuracy was within 5%, as demonstrated by reference measurements of a well-defined ammonia transition. The results show that the presented method is well suited to measure atomic oxygen densities, and it closes the THz gap for quantitative atomic density measurements in harsh environments such as plasmas.