dc.creator Hodges, James N. en_US dc.creator Perry, Adam J. en_US dc.creator Siller, Brian M. en_US dc.creator McCall, Benjamin J. en_US dc.date.accessioned 2013-07-16T21:47:37Z dc.date.available 2013-07-16T21:47:37Z dc.date.issued 2013 en_US dc.identifier 2013-MG-06 en_US dc.identifier.uri http://hdl.handle.net/1811/55599 dc.description Author Institution: Department of Chemistry, University of Illinois, Urbana, IL 61801; Departments of Chemistry, Astronomy, and Physics, University of Illinois, Urbana, IL 61801 en_US dc.description.abstract Spectroscopy of H$_3^+$ is of fundamental interest for advancing \textit{ab initio} efforts to calculate spectra with high precision and accuracy. H$_3^+$ is the simplest polyatomic ion, which is why it is an excellent benchmark for theory. In order to perform calculations with spectroscopic accuracy, relativistic and non-adiabatic corrections to the Born-Oppenhiemer approximation must be included; calculations with these considerations agree to within hundredths of a wavenumber. (1999), \textbf{110}, 5056--5064.} Increasing the precision of the calculations further will require a treatment of quantum electrodynamic effects, as has already been implemented for the diatomic case, \emph{J. Chem. Theor. Comp.} (2011), \textbf{7}, 3105--3115.} and testing these calculations will require higher-precision experimental data to guide \textit{ab initio} calculations. \vspace{1em} Noise Immune Cavity Enhanced Optical Heterodyne Velocity Modulation Spectroscopy, or NICE-OHVMS \emph{Opt. Express} (2011), \textbf{19}, 24822--7.} \emph{Chem. Phys. Lett.} (2012), \textbf{551}, 1--6.}, is a highly sensitive, highly precise technique that we have employed to observe transitions in the $\nu_2$ fundamental band of H$_3^+$. It combines the advantages of cavity enhancement and heterodyne detection with the ion-neutral discrimination afforded by velocity modulation. Combining a cavity with a high power mid-infrared light source, we can saturate rovibrational transitions. The resulting Lamb dips may be fit in order to determine line centers to a much higher precision than is possible for ordinary Doppler broadened profiles. Additionally, a frequency comb is used to surpass the limited accuracy and precision of a wavemeter. Here we present the results from comb calibrated H$_3^+$ transitions observed via NICE-OHVMS. Precision and accuracy of $\sim$ 1 MHz were achieved representing the most accurate and precise H$_3^+$ line list that has been obtained to date. en_US dc.language.iso en en_US dc.publisher Ohio State University en_US dc.title SUB-DOPPLER SPECTROSCOPY OF H$_3^+$ en_US dc.type Article en_US dc.type Image en_US dc.type Presentation en_US
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