Toward a global model of the interactions in low-lying states of methyl cyanide: rotational and rovibrational spectroscopy of the $v_4=1$ state and tentative interstellar detection of the $v_4=v_8=1$ state in Sgr B2(N)

Abstract

New and existing rotational spectra of methyl cyanide were analyzed to extend the global model of low-lying vibrational states and their interactions to $v_4=1$ at 920 cm${}^{-1}$. The rotational spectra cover large portions of the 36$-$1439 GHz region and reach quantum numbers $J$ and $K$ of 79 and 16, respectively. Information on the $K$ level structure of CH${}_3$CN is obtained from IR spectra. A spectrum of $2{\nu }_8$ around 717 cm${}^{-1}$, analyzed in our previous study, covered also the ${\nu }_4$ band. The assignments in this band cover 880$-$952 cm${}^{-1}$, attaining quantum numbers $J$ and $K$ of 61 and 13, respectively. The most important interaction of $v_4=1$ appears to be with $v_8=3$, $\Delta K=0$, $\Delta l=+3$, a previously characterized anharmonic resonance. We report new analyses of interactions with $\Delta K=-2$ and $\Delta l=+1$, with $\Delta K=-4$ and $\Delta l=-1$, and with $\Delta K=-6$ and $\Delta l=-3$; these four types of interactions connect all $l$ substates of $v_8=3$ in energy to $v_4=1$. A known $\Delta K=-2$, $\Delta l=+1$ interaction with $v_7=1$ was also analyzed, and investigations of the $\Delta K=+1$, $\Delta l=-2$ and $\Delta K=+3$, $\Delta l=0$ resonances with $v_8=2$ were improved, as were interactions between successive states with $v_8\le 3$, mainly through new $v_8\le 2$ rotational data. A preliminary single state analysis of the $v_4=v_8=1$ state was carried out based on rotational transition frequencies and on ${\nu }_4+{\nu }_8-{\nu }_8$ hot band data. A considerable fraction of the $K$ levels was reproduced within uncertainties in its entirety or in part, despite obvious widespread perturbations in $v_4=v_8=1$. We detect rotational transitions of methyl cyanide from within all vibrational states up to $v_4=1$ and $v_4=v_8=1$ tentatively toward the hot molecular core of Sagittarius B2(N) employing the Atacama Large Millimeter Array.

arXiv comment30 pages, J. Mol. Spectrosc., accepted

References in corpus (16)

• The Cologne Database for Molecular Spectroscopy, CDMS, in the Virtual Atomic and Molecular Data Centre, VAMDC
• Trigonometric Parallaxes Of High-Mass Star Forming Regions: Our View Of The Milky Way
• Exploring Molecular Complexity with ALMA (EMoCA): Deuterated complex organic molecules in Sagittarius B2(N2)
• Weeds: a CLASS extension for the analysis of millimeter and sub-millimeter spectral surveys
• Re-exploring Molecular Complexity with ALMA (ReMoCA): Interstellar detection of urea
• Exploring molecular complexity with ALMA (EMoCA): Alkanethiols and alkanols in Sagittarius B2(N2)
• The ALMA-PILS survey: Complex nitriles towards IRAS 16293--2422
• The complex chemistry of hot cores in Sagittarius B2(N): Influence of cosmic-ray ionization and thermal history
• Rotational spectroscopy of isotopic vinyl cyanide, H${}_2$C=CH$-$C$\equiv$N, in the laboratory and in space
• Rotational spectra of isotopic species of methyl cyanide, CH${}_3$CN, in their ground vibrational states up to terahertz frequencies
• Rotational spectroscopy as a tool to investigate interactions between vibrational polyads in symmetric top molecules: low-lying states $v_8\le 2$ of methyl cyanide, CH${}_3$CN
• Far-infrared laboratory spectroscopy of aminoacetonitrile and first interstellar detection of its vibrationally excited transitions
• The quest for complex molecules in space: Laboratory spectroscopy of n-butyl cyanide, n-C4H9CN, in the millimeter wave region and its astronomical search in Sagittarius B2(N)
• Laboratory spectroscopic study of isotopic thioformaldehyde, H${}_2$CS, and determination of its equilibrium structure
• Millimeter- and submillimeter-wave spectroscopy of thioformamide and interstellar search toward Sgr B2(N)
• Rotational spectra of isotopic species of methyl cyanide, CH${}_3$CN, in their $v_8=1$ excited vibrational states

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• Shocking Sgr B2(N1) with its own outflow: A new perspective on segregation between O- and N-bearing molecules
• Rotational spectroscopy of CH${}_3$OD with a reanalysis of CH${}_3$OD toward IRAS 16293$-$2422
• Rotational spectroscopy of oxirane-\textit{2,2}-$d_2$, $c$-CD${}_2$CH${}_2$O, and its tentative detection toward IRAS 16293$-$2422~B
• Investigation of the rotational spectrum of CD${}_3$OD and an astronomical search toward IRAS 16293$-$2422
• Rotation-tunneling spectrum and astrochemical modeling of dimethylamine, CH${}_3$NHCH${}_3$, and searches for it in space
• The salty emission of the intermediate-mass AGB star OH 30.1 -0.7
• Submillimeter-wave spectroscopy of the CH${}_3$O radical
• Rotational spectroscopy of the thioformaldehyde isotopologues H${}_2$CS and H${}_2$C${}^{34}$S in four interacting excited vibrational states and an account on the rotational spectrum of thioketene, H${}_2$CCS
• Investigation of the rotational spectrum of CH${}_3$${}^{17}$OH and its tentative detection toward Sagittarius B2(N)
• Rotational Spectroscopy as a Tool to Study Vibration-Rotation Interaction: Investigations of ${}^{13}$CH${}_3$CN and CH${}_3$${}^{13}$CN up to $v_8=2$ and a Search for $v_8=2$ Transitions toward Sagittarius B2(N)