Journal of Quantitative Spectroscopy & Radiative Transfer 255 (2020) 107254 Contents lists available at ScienceDirect Journal of Quantitative Spectroscopy & Radiative Transfer journal homepage: www.elsevier.com/locate/jqsrt High-resolution and -precision spectra of acetonitrile at the ν 5 -band for laser remote sensing Hongfei Guan a,b,1 , Xiaoyu Wang a,1 , Ruiyan Han a , Liming Yuan a , Shuo Meng a , Shuanke Wang a , Zhenhui Du a,∗ a State Key Laboratory of Precision Measuring Technology and Instruments, Tianjin University, No.92, Weijin Road, Tianjin 300072, China b Key Laboratory of Space Utilization, Technology and Engineering Center for Space Utilization, Chinese Academy of Science, Beijing 100094, China a r t i c l e i n f o Article history: Received 25 May 2020 Revised 27 July 2020 Accepted 10 August 2020 Available online 20 August 2020 Keywords: High-resolution and -precision spectra Acetonitrile Tunable laser absorption spectroscopy (TLAS) a b s t r a c t Ultrahigh-resolution and -precision air-broadened acetonitrile (CH 3 CN) spectra of the v 5 -band in the re- gion of 3039.0–3041.5 cm −1 were recorded and analyzed using tunable laser absorption spectroscopy (TLAS) technology with a distributed feedback interband cascade laser. The spectral line profile of methane (CH 4 ) was used as the standard to correct the nonlinearity and baseline drift in the CH 3 CN spectra. The recorded spectra are very close to that in the Pacific Northwest National Laboratory (PNNL) database, however it has a much lower absorbance uncertainty of 1.02%. The air-broadened CH 3 CN ab- sorption at the v 5 -band with a spectral resolution of 2.15 × 10 −5 cm −1 (~23 fm/637 kHz) and an es- timated uncertainty of 1.1% was derived at a temperature of 296.75 K and a pressure of 1 atm. The ultrahigh-resolution and -precision spectra of CH 3 CN provide reference data for absolute spectral mea- surements, laser remote sensing, and atmospheric inversion. © 2020 Elsevier Ltd. All rights reserved. 1. Introduction Acetonitrile (methyl cyanide, ethanenitrile, CH 3 CN), a toxic col- orless flammable gas, is widely used as a solvent in the chem- ical industry. It naturally exists on the Earth [1–3], in molecu- lar clouds, and in planetary atmospheres [4,5]. CH 3 CN is a use- ful tracer for biomass burning and atmospheric transport processes [1,2] with a lifetime of approximately days to months for reac- tion with atmospheric hydroxyl radicals and/or ozone. The pub- lished data of in-situ measurements of CH 3 CN in urban/rural en- vironments were sporadic and often conflicting [6]. A mean atmo- spheric residence time of 6.6 months for CH 3 CN by Singh et al. [6] assuming loss to the oceans and reaction with OH radicals as the major removal processes. While, 1-month lifetime of CH 3 CN by Bange and Williams [7]. CH 3 CN is harmful and sometimes lethal to the environment and human body [8]. Sensitive and selective re- mote laser detection of CH 3 CN in practical conditions is needed, in which high-quality reference spectral data are essential. The need for high-quality reference spectral data of CH 3 CN has been desired for some time. Harrison et al. [9] obtained the spec- trum of CH 3 CN in dry synthetic air with a wavenumber resolu- ∗ Corresponding author E-mail address: duzhenhui@tju.edu.cn (Z. Du). 1 These authors contributed equally. tion of 0.015 cm −1 at 50–760 Torr and 203–297 K, while deriv- ing the spectral region between 880 and 1700 cm −1 . Subsequently, Allen et al. [10] recorded eleven CH 3 CN spectra at 1 atm and 207–296 K with a wavenumber resolution of 0.015 cm −1 , covering the range of 2400–3500 cm −1 , with an estimated uncertainty of 2% of the cross section and an overall uncertainty of the absorp- tion cross section of 4%. Although these CH 3 CN spectral data are air-broadened, the spectral resolution is still insufficient for tun- able laser spectroscopy. Rinsland et al. [11] used a Bruker-66 V Fourier transform IR spectrometer (FT-IR) to measure the absorp- tion cross sections of CH 3 CN in nitrogen covering a range of 600– 6500 cm −1 at 1 atm and 276 K, 298 K, and 323 K, with a spectral resolution of only 0.112 cm −1 . These recorded CH 3 CN spectra [9– 11] were indexed in the HITRAN (High Resolution Transmission) 2016 database. Chu et al. [12] measured the spectral data of vapor- phase CH 3 CN in nitrogen, which covered a range of 575–3975 cm −1 at 101.3 kPa and 296 K, with spectral resolution of 0.125 cm −1 and accuracy of 0.0042 cm −1 ; the uncertainty of the ab- sorption coefficient was 2.2%, which was indexed in NIST. Although the wave number range was expanded [11,12], the spectral resolu- tion and accuracy were still too low for laser sensing applications. Therefore, there is a lack of high-resolution mid-infrared spec- tral data in existing databases for the Earth’s atmospheric applica- tions [11], so it is important to obtain higher-resolution absorption spectra of CH 3 CN. For laser gas spectrometers (LGSs), high-quality https://doi.org/10.1016/j.jqsrt.2020.107254 0022-4073/© 2020 Elsevier Ltd. All rights reserved.