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Title: Femtosecond ultraviolet laser absorption spectroscopy for simultaneous measurements of temperature and OH concentration
This Letter reports a femtosecond ultraviolet laser absorption spectroscopy (fs-UV-LAS) for simultaneous in situ measurements of temperature and species. This fs-UV-LAS technique was demonstrated based on X 2 Π-A 2 Σ + transitions of OH radicals near 308 nm generated in low temperature plasmas and flames. The fs-UV-LAS technique has revealed three major diagnostic benefits. First, a series of absorption features within a spectral bandwidth of ∼3.2 nm near 308 nm were simultaneously measured and then enabled simultaneous multi-parameter measurements with enhanced accuracy. The results show that the temperature and OH concentration could be measured with accuracy enhanced by 29–88% and 58–91%, respectively, compared to those obtained with past two-narrow-line absorption methods. Second, an ultrafast time resolution of ∼120 picoseconds was accomplished for the measurements. Third, due to the large OH X 2 Π-A 2 Σ + transitions in the UV range, a simple single-pass absorption with a 3-cm path length was allowed for measurements in plasmas with low OH number density down to ∼2 × 10 13  cm −3 . Also due to the large OH UV transitions, single-shot fs absorption measurements were accomplished in flames, which was expected to offer more insights into chemically reactive flow dynamics.  more » « less
Award ID(s):
1903362 2029425
NSF-PAR ID:
10347159
Author(s) / Creator(s):
; ; ; ; ;
Date Published:
Journal Name:
Applied Physics Letters
Volume:
120
Issue:
20
ISSN:
0003-6951
Page Range / eLocation ID:
201103
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
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