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 Title: MOLECULAR LINE PARAMETERS PRECISELY DETERMINED BY A CAVITY RING-DOWN SPECTROMETER Author(s): Hu, Shui-Ming Contributor(s): Liu, An-Wen; Sun, Yu Robert; Cheng, Cunfeng; Lu, Yan; Wang, Jin; Tan, Yan Subject(s): Mini-symposium: High-Precision Spectroscopy Abstract: A cavity ring-down spectrometer calibrated with a set of precise atomic lines was built to retrieve precise line parameters in the near infrared.~[1,2] The spectrometer allows us to detect absorptions with a sensitivity of $10^{-11}$~cm$^{-1}$ and a spectral precision up to $10^{-6}$~cm$^{-1}$. Ro-vibrational lines in the second overtone of H$_2$ have been observed, including the extremely weak S$_3$(5) line with a line intensity less than $1times 10^{-30}$cm/molecule, which is among the weakest molecular lines detected by absorption in the gas phase. The absolute line positions of H$_2$ agree well with the high-level quantum chemical calculations including relativistic and QED corrections, with the deviation being less than $5times 10^{-4}$~cm$^{-1}$.~[3,4] A quantitative study has also been carried out on the $nu_1+5nu_3$ band of CO$_2$.~[5] It was the first CO$_2$ band observed 80 years ago in the spectrum of Venus. We determined the line positions with an accuracy of $3times 10^{-5}$~cm$^{-1}$, two orders of magnitude better than previous studies. Similar studies have been carried out to determine the line parameters of H$_2$O~[6] and CO~[7] in the spectral regions near 0.8~$mu$m. The spectroscopic parameters can be used in varies studies, from the atmospheres of the earth-like planets to the test of fundamental physics. vspace{0.1in} noindent textbf{References} noindent [1] H. Pan, textit{et al.} Rev. Sci. Instrum. textbf{82}, 103110 (2011). noindent [2] C.-F. Cheng, Opt. Expr. textbf{20}, 9956 (2012). noindent [3] C.-F. Cheng, textit{et al.} Phys. Rev. A textbf{85}, 024501 (2012). noindent [4] y. Tan, textit{et al.} J. Mol. Spectrosc. textbf{300}, 60 (2014). noindent [5] Y. Lu, textit{et al.} Astrophys. J. textbf{775}, 71 (2013). noindent [6] Y. Lu, textit{et al.} JQSRT textbf{118}, 96 (2013). noindent [7] Y. Tan, textit{et al.} Ro-vibrational analysis of the fifth overtone of CO at 802~nm'', under preparation. Issue Date: 24-Jun-15 Publisher: International Symposium on Molecular Spectroscopy Citation Info: ACS Genre: CONFERENCE PAPER/PRESENTATION Type: Text Language: English URI: http://hdl.handle.net/2142/79408 Date Available in IDEALS: 2016-01-05
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