Measurement Of The Lowest Millimeter-wave Transition Frequency Of The Ch Radical

Truppe, Stefan

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https://hdl.handle.net/2142/51054 Copy

Description

Title

Measurement Of The Lowest Millimeter-wave Transition Frequency Of The Ch Radical

Author(s)

Truppe, Stefan

Contributor(s)

• Tarbutt, Michael
• Hinds, Ed
• Hendricks, Richard James

Issue Date

2014-06-18

Keyword(s)

Mini-symposium: Astronomical Molecular Spectroscopy in the Age of ALMA

Abstract

The CH radical is an important constituent of stellar atmospheres, interstellar gas clouds and is of fundamental importance to interstellar chemistry. Furthermore, it offers a sensitive way to test the hypothesis that fundamental constants measured on earth may differ from those observed in other parts of the universe\footnote{S. Truppe et al., \textit{Nature Communications}~\underline{\textbf{4}}, 2600, 2013}. Here, we present a measurement of the lowest millimeter-wave transition of CH, near 535~GHz, with an accuracy of 0.6~kHz\footnote{S. Truppe et al., \textit{The Astrophysical Journal}~\underline{\textbf{780}}, 71, 2014}, an improvement of nearly two orders of magnitude compared to the previous best rest frequencies. We drive the millimeter-wave transitions using the 54th harmonic of a frequency synthesizer phase-locked to a 10 MHz GPS frequency reference. Using ALMA this transition has recently been observed in the absorber PKS 1830-211 at a redshift of $z=0.89$\footnote{S. Muller, \textit{private communication}, 2013}. As pointed out by de Nijs et al.\footnote{de Nijs et al., \textit{Physical Review A}~\underline{\textbf{86}}, 032501, 2012} a very robust and sensitive means to search for variations in fundamental constants could be obtained by observing the lowest millimeter-wave transition of CH along with the two $\Lambda$-doublets at 3.3 and 0.7~GHz, all from the same interstellar gas cloud.

Publisher

International Symposium on Molecular Spectroscopy

Type of Resource

text

Language

English

Permalink

http://hdl.handle.net/2142/51054

DOI

https://doi.org/10.15278/isms.2014.WF05

Copyright and License Information

Copyright 2014 by the authors. Licensed under a Creative Commons Attribution 4.0 International License. http://creativecommons.org/licenses/by/4.0/

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