AUTHOR=Schmid Philipp C. , Thorwirth Sven , Endres Christian P. , Töpfer Matthias , Sánchez-Monge Álvaro , Schwörer Andreas , Schilke Peter , Schlemmer Stephan , Asvany Oskar 

TITLE=Rotational Rest Frequencies and First Astronomical Search of Protonated Methylamine

JOURNAL=Frontiers in Astronomy and Space Sciences

VOLUME=8

YEAR=2022

URL=https://www.frontiersin.org/journals/astronomy-and-space-sciences/articles/10.3389/fspas.2021.805162

DOI=10.3389/fspas.2021.805162

ISSN=2296-987X

ABSTRACT=<p>We report first laboratory rest frequencies for rotational transitions of protonated methylamine, <inline-formula id="inf1"><mml:math id="m1" xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mrow><mml:mi mathvariant="normal">C</mml:mi><mml:mi mathvariant="normal">H</mml:mi></mml:mrow><mml:mrow><mml:mn>3</mml:mn></mml:mrow></mml:msub><mml:msup><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">N</mml:mi><mml:mi mathvariant="normal">H</mml:mi></mml:mrow><mml:mrow><mml:mn>3</mml:mn></mml:mrow></mml:msub></mml:mrow><mml:mrow><mml:mo>+</mml:mo></mml:mrow></mml:msup></mml:math></inline-formula>, measured in a cryogenic 22-pole ion trap machine and employing an action spectroscopy scheme. For this prolate symmetric top molecule thirteen transitions between 80 and 240 GHz were detected in the ground vibrational state, covering <italic>J</italic><sub><italic>K</italic></sub> = 2<sub><italic>K</italic></sub> − 1<sub><italic>K</italic></sub> up to <italic>J</italic><sub><italic>K</italic></sub> = 6<sub><italic>K</italic></sub> − 5<sub><italic>K</italic></sub> with <italic>K</italic> = 0, 1, 2. Some transitions exhibit noticeable structure that is attributed to internal rotation splitting. As the CN radical and several of its hydrogenated and protonated forms up to methylamine, CH<sub>3</sub>NH<sub>2</sub>, are well known entities in the laboratory and in space, protonated methylamine, <inline-formula id="inf2"><mml:math id="m2" xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mrow><mml:mi mathvariant="normal">C</mml:mi><mml:mi mathvariant="normal">H</mml:mi></mml:mrow><mml:mrow><mml:mn>3</mml:mn></mml:mrow></mml:msub><mml:msup><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">N</mml:mi><mml:mi mathvariant="normal">H</mml:mi></mml:mrow><mml:mrow><mml:mn>3</mml:mn></mml:mrow></mml:msub></mml:mrow><mml:mrow><mml:mo>+</mml:mo></mml:mrow></mml:msup></mml:math></inline-formula>, is a promising candidate for future radio astronomical detection.</p>