%% *-----------------------------------------------------------------------------------------*
\documentclass[11pt]{article}

\usepackage{hrms}  %% Page settings, style ... for the HRMS abstract book.

%% *-----------------------------------------------------------------------------------------*

\title{COMPOSITE ABSORPTION CROSS SECTIONS AND INTEGRATED BAND INTENSITIES OF CHF$_3$ IN SYNTHETIC AIR}


\author{\underline{\FirstName K. \LastName BEREZKIN},
  \FirstName A. \LastName DOMANSKAYA, \FirstName H. \LastName BOHLIUS, \FirstName M.E. \LastName KIM, 
\FirstName G. \LastName LI, and \FirstName V. \LastName EBERT}

\address{Physikalisch-Technische Bundesanstalt (PTB), Bundesallee 100, 38116 Braunschweig, Germany}


%% *-----------------------------------------------------------------------------------------*

\usepackage{fancyhdr}
\pagestyle{fancy}
\fancyhead[C]{{\footnotesize \textit{HRMS, 28th Colloquium, Dijon, France,
  Aug. 28 - Sept. 1, 2023}}}
\fancyfoot[C]{}
\renewcommand{\headrulewidth}{0.6pt}
\renewcommand{\footrulewidth}{0.6pt}

\usepackage[colorlinks=true,urlcolor=blue,linkcolor=blue,citecolor=blue]{hyperref}
\voffset -.65 cm

%% *-----------------------------------------------------------------------------------------*

\category {3,9}
\category {3,9}
\begin{document}

\maketitle  %% This will also build the list of author(s) and addresse(s).


\index{trifluoromethane}
\index{infrared intensity}

CHF$_3$ (fluoroform, trifluoromethane, HFC-23, CAS no: 75-46-7) is a strong potent greenhouse gas (GWP-100 = 14600), 
with its atmospheric amount fraction increasing by 0.75 $\pm$ 0.02 pmol\slash mol\slash year\footnote{\href{http://dx.doi.org/10.1016/j.jqsrt.2019.06.019}{10.1016/j.jqsrt.2019.06.019}, A. M. Fernando, P. F. Bernath, C. D. Boone, {\it JQSRT\/}, {\bf 
238}, 106540 (2019).}. It is not only a byproduct of the synthesis of CHClF$_2$ but is also used in the semiconductor industry and as a low-temperature refrigerant.

CHF$_3$ is an oblate symmetric top molecule (C$_{3v}$ point group) with three totally symmetric vibrations ($\nu_1$, $\nu_2$, $\nu_3$) and three doubly degenerate vibrations ($\nu_4$, $\nu_5$, $\nu_6$).
 Its congested absorption spectra contain not only transitions from ground state and hot bands for main isotopologue (${}^{12}$CHF$_3$),
 but also information on ${}^{13}$CHF$_3$, which bands appear nearby. Absorption in the region of $\nu_2$/$\nu_5$ dyad occurs in the atmospheric transparency window and is used for remote sensing.

In the current work, we recorded several spectra with different compositions of CHF$_3$ mixtures with synthetic air to reconstruct the cumulative spectrum at 296 K
 in the region of 550--2000 cm$^{-1}$. A similar algorithm was used in our work with CF$_4$ and SF$_6$ and in the PNNL
 database\footnote{\href{http://dx.doi.org/10.1366/0003702042641281}{10.1366/0003702042641281}, S.W. Sharpe et al., {\it App. Spectrosc.\/}, {\bf 58}(12), 1452--1461 (2004).}.
 CHF$_3$ turned out to be a more challenging molecule since the contribution of the self-broadening becomes visible already at absorber dilution ratios exceeding 1$\%$.
 This can lead to distortion (broadening) of the cumulative absorption cross sections compared to those corresponding to strongly diluted samples. Nevertheless, adding concentrated samples to the average does not affect the integrated intensities.

We report on the integrated intensities in the region of the $\nu_3$, $\nu_2$/$\nu_5$ and $\nu_4$  fundamental bands together with the overtone band of $\nu_6$ 
and two combinations that involve $\nu_2$ band, namely $\nu_2+\nu_6$ and $\nu_2+\nu_3$. The expanded uncertainties ($k=2$) are below $1.8 \%$ for the reported fundamental bands. 

The measurements and analysis were performed within the frame of the EMPIR project ''Metrology for Climate Relevant Volatile Organic Compounds'' (MetClimVOC)\footnote{EMPIR project ''Metrology for climate relevant volatile organic compounds'', (\href{www.metclimvoc.eu}{MetClimVOC}).}. 
The spectra were recorded using a Bruker-125 HR spectrometer at the PTB EUMETRICSPEC infrastructure\footnote{Spectral reference data for atmospheric monitoring, (\href{https://www.eumetrispec.org/}{EUMETRISPEC}).}.


\end{document}
