The unambiguous identification of biomarkers on icy/subsurface ocean worlds in our solar system is an important goal of current astrobiology. Mass spectrometry techniques implemented on planetary probes are useful, but unable to distinguish between isomers with the same atomic composition. By combining mass spectrometry and infrared spectroscopy, isomers can be unambiguously detected and distinguished. Cryogenic Ion Vibrational Spectroscopy (CIVS) using messenger tagging combines these techniques to produce well-resolved spectra of mass-selected ions. We present results on the spectroscopy of protonated niacinamide using CIVS. Peaks are assigned with the use of harmonic and anharmonic density functional theory calculations. The authors gratefully acknowledge support from a JPL/NASA Strategic University Research Partnership Grant and from the National Science Foundation (CHE-2154271).html:<hr /><h3>Footnotes: The authors gratefully acknowledge support from a JPL/NASA Strategic University Research Partnership Grant and from the National Science Foundation (CHE-2154271).

Low temperature reactions of the CN radical with unsaturated hydrocarbons are important for understanding the chemistry of hot molecular cores and the nitrogen rich atmosphere of satellites such as Titan. The reactions of the CN radical with unsaturated hydrocarbons are also important for understanding the combustion of hydrocarbons with a nitrogen source. The CN radical is produced by the pyrolysis of ICN. Acetylene and the CN radical are sequentially doped into a beam of superfluid helium nanodroplets and are probed with an infrared action spectroscopy in the C-H stretching region. Due to rapid cooling and low temperature (0.38 K), this technique is particularly suited for studying entrance channel complexes with very low barrier heights. Evidence for a linear CN-C2H2 complex is found, and the C-H stretching region of this complex is discussed.

Polycyclic aromatic hydrocarbons (PAHs) are believed to be the carriers of the aromatic infrared bands (AIBs) and have been proposed as candidates to explain other astronomical phenomena such as diffuse interstellar bands (DIBs).A. G. G. M. Tielens, Annual Review of Astronomy and Astrophysics, 46, 289, 2008. W. W. Duley, Faraday discussions, 133, 415, 2006.he first aromatic structures possessing more than one ring, 1- and 2-cyanonaphthalene (1-, 2-CNN), were recently detected by rotational spectroscopy in the dense molecular cloud TMC-1.B. A. McGuire et al Science, 371, 6535, 1265–1269, 2021.aboratory investigations have indicated that due to fast and efficient relaxation through recurrent fluorescence, CNN⁺ may be photostable in the harsh conditions of the lower density, more diffuse regions of the interstellar medium (ISM) exposed to ultraviolet radiation.M. H. Stockett et al, Nature Communications, 14, 395, 2023.s a result, the widely held belief that small PAHs present in these regions are dissociated, may need to be revisited. If 1-CNN⁺ is able to survive in the diffuse ISM it may contribute to the population of 1-CNN observed in TMC-1. To investigate the abundance of 1-CNN⁺ in diffuse clouds, spectroscopic measurements are required. The present work concerns the gas-phase electronic spectroscopic experiments of 1-CNN⁺, carried out using a cryogenic ion trapping apparatus at temperatures below 10 K through buffer gas cooling.E.K. Campbell et al The Astrophysical Journal, 822, 17, 2016.n this presentation, the electronic transitions D₀ to D₂ and D₀ to D₃ are discussed, complemented by time-dependant DFT calculations. The D₀ to D₂ transition has a calculated oscillator strength of f = 0.075, dominated by its origin band. The origin band possesses a peak maximum at 7343 Å with a full width at half maximum of 28 Å, which is compared to observational data.

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A. G. G. M. Tielens, Annual Review of Astronomy and Astrophysics, 46, 289, 2008., W. W. Duley, Faraday discussions, 133, 415, 2006.T B. A. McGuire et al Science, 371, 6535, 1265–1269, 2021.L M. H. Stockett et al, Nature Communications, 14, 395, 2023.A E.K. Campbell et al The Astrophysical Journal, 822, 17, 2016.I

The electron affinities (EAs) of a series of C₆H_5−xF_X (1 ≤ x ≤ 4) fluorophenyl radicals are determined from the photoelectron spectra of their associated fluorophenide anions generated from C₆H_6−xF_X (1 ≤ x ≤ 4) fluorobenzene precursors. The spectra show a near-linear incremental increase in EA of 0.4 eV/x. The spectra exhibit vibrationally unresolved and broad detachment transitions consistent with significant differences in the molecular structures of the anion and neutral radical species. The experimental EAs and broad spectra are consistent with density functional theory calculations on these species. While the anion detachment transitions all involve an electron in a non-bonding orbital, the differences in structure between the neutral and anion are in part due to repulsion between the lone pair on the C-center on which the excess charge is localized and neighboring F atoms. The C₆H_5−xF_X (2 ≤ x ≤ 4) spectra show features at lower binding energy that appear to be due to constitutional isomers formed in the ion source.

Large radicals are known as the main reactants of a complex network of chemical reactions leading to the formation of complex organic molecules (COMs) detected in the interstellar medium Scibelli, Shirley, The Astrophysical Journal, 891 73 (2020) They are also important intermediates in atmospheric and combustion chemistry Alam, Rickard, Camredon, Wyche, Carr, Hornsby, Monks, Bloss, The Journal of Physical Chemistry A, 117 12468 (2013) In this talk, a methodology to study specific dehydrogenated COMs in the gas phase will be described using the example of our recent spectroscopic investigation concerning the acetonyl radical, CH₃COCH₂, at millimeter and sub-millimeter wavelengths (160-450 GHz). The radical detection is performed using Faraday rotation modulation spectroscopy, allowing the detection of paramagnetic species only and the discrimination of the spin rotation components for each transition Viciani, De Natale, Gianfrani, Inguscio, Optical Society of America, 16 301 (1999) Thanks to the very broad spectral ranges covered in our recordings, we could rapidly identify series of lines using Loomis-Wood graphical representation Bonah, Zingsheim, Müller, Guillemin, Lewen, Schlemmer, Journal of Molecular Spectroscopy, 388 111674 (2022)o perform the rotational assignment. I will present the instrumental developments and the methodology used to analyze the acetonyl radical. This methodology will be applied to many other large radical species in the near future.

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Scibelli, Shirley, The Astrophysical Journal, 891 73 (2020). Alam, Rickard, Camredon, Wyche, Carr, Hornsby, Monks, Bloss, The Journal of Physical Chemistry A, 117 12468 (2013). Viciani, De Natale, Gianfrani, Inguscio, Optical Society of America, 16 301 (1999). Bonah, Zingsheim, Müller, Guillemin, Lewen, Schlemmer, Journal of Molecular Spectroscopy, 388 111674 (2022)t

l0pt Figure The 2-pyridoxy (C₅H₄NO) radical has an extensively complex microwave spectrum owing to the multitude of interactions between the spin angular momentum of its unpaired electron, the 1/2 nuclear spin angular momentum of its four hydrogen nuclei, the 1 nuclear spin angular momentum of its nitrogen nucleus and the overall rotation of the molecule itself. We have measured the microwave spectrum of the 2-pyridoxy radical from 8 – 18 GHz utilizing a chirped-pulse Fourier transform microwave (CP-FTMW) spectrometer. 2-pyridoxy radicals were formed in an electrical discharge arced across a supersonic expansion seeded with 2-methoxypyridine. We will present our investigation into how the spectral structure of 2-pyridoxy can be used as a sensitive probe for the angular momentum coupling and extent of delocalization of the unpaired electron. Such spectroscopic characterization may also yield mechanistic insight into nitrogen-containing heterocyclic reactive intermediates, which are of key importance in both combustion¹ and astrochemical² environments. This work was supported by the Gas Phase Chemical Physics program of the Department of Energy, Office of Science, Basic Energy Sciences.
[1] Glarborg, P. Fuel nitrogen conversion in solid fuel fired systems. Prog. Energy Combust. Sci. 2003, 29, 89-113. [2] Martins, Z. The nitrogen heterocycle content of meteorites andtheir significance for the origin of life. Life 2018, 8, No. 28

In the interstellar medium a large abundance of molecules could be detected to this day. In this context hydrogen cyanide HCN and its isomer HNC are thoroughly studied molecules, but very little is known spectroscopically about their cations, HCN⁺ and HNC⁺ respectively. As these open-shell cations are very reactive, the detection of their spectra in the laboratory was very challenging.
In this contribution we present the first measurements on the high-resolution ro-vibrational spectra of HCN⁺ and HNC⁺ in a cryogenic 22-pole ion trap (LIRtrap) in combination with the novel leak-out spectroscopy (LOS) technique P.C. Schmid et al., J. Phys. Chem. A 126(2022)8111. For the HCN⁺ cation the C-H ν₁ fundamental band was measured at 10 K as well as 4 K. Both the F₁ and F₂ spin-orbit components as well as Λ-doubling (e/f) were resolved in the recorded spectra. Additionally, the ν₁+ν₂ combination band could be observed. Using the ro-vibrational transitions assigned within both bands, highly accurate spectroscopic parameters have been determined for HCN⁺. Based on these constants we recorded the first pure rotational spectrum of HCN⁺ see talk by Weslley G.D.P. Silva at this conference
For lower energy isomer HNC⁺, the N-H ν₁ fundamental band was recorded in high-resolution. Accurate spectroscopic constants were also determined, which will allow us to detect its pure rotational spectrum in future measurements. Apart from recording molecular spectra in high-resolution, LOS allows for the preparation of a pure isomeric sample. Here we further show the formation of a clean sample of either HCN⁺ or HNC⁺ within the cryogenic ion trap using the spectroscopy controlled cleaning of the sample. This will enable us to study the influence of the isomeric structure of these open-shell cations in gas-phase reactions with isomeric pure samples.

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P.C. Schmid et al., J. Phys. Chem. A 126(2022)8111.. see talk by Weslley G.D.P. Silva at this conference.

The rotational spectra of HCNH⁺ and HCN⁺ were measured in a 22-pole cryogenic ion trap instrument employing a vibrational-rotational double resonance scheme based on the novel leak-out spectroscopy method.P. C. Schmid, O. Asvany, T. Salomon, S. Thorwirth and S. Schlemmer, J. Phys. Chem. A 126, 43 (2002)or the well-known closed-shell HCNH⁺ molecule (X̃¹Σ⁺), we re-measured the first six rotational transitions between 70 and 450 GHz, which were readily identified based on previous reports.L. M. Ziurys and B. E. Turner, Astrophys. J. Lett. 302, L31 (1986); L. M. Ziurys, A. J. Apponi, and J. T. Yoder, Astrophys. J. Lett. 397, L123 (1992); T. Amano, K. Hashimoto, and T. Hirao, J. Mol. Struct. 795, 190–193 (2006)iven the cryogenic temperature of the trap, the hyperfine splittings due to the ¹⁴N quadrupolar nucleus (I = 1) could be resolved for the first time in the laboratory for transitions up to J = 4.W. G. D. P. Silva, L. Bonah, P. C. Schmid, S. Schlemmer, O. Asvany, J. Chem. Phys. 160, 071101 (2024)his allowed for a refinement of the spectroscopic parameters of this important interstellar molecule, including the quadrupole coupling constant eQq for ¹⁴N. For the open-shell HCN⁺ cation (X̃²Π), four rotational transitions within the lower energy spin-orbit F₁ component were observed between 270 and 520 GHz. The Λ-doubling components (e and f) are well-resolved for all observed transitions and each displays extensive and complex hyperfine structure due to both the ¹⁴N (I = 1) and the H (I = 1/2) nuclei. This marks the first report on the pure rotational spectrum of HCN⁺. The laboratory measurements reported here will allow the first radio astronomical search for HCN⁺ and may permit additional hyperfine splittings of HCNH⁺ to be detected in the interstellar medium.

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P. C. Schmid, O. Asvany, T. Salomon, S. Thorwirth and S. Schlemmer, J. Phys. Chem. A 126, 43 (2002)F L. M. Ziurys and B. E. Turner, Astrophys. J. Lett. 302, L31 (1986); L. M. Ziurys, A. J. Apponi, and J. T. Yoder, Astrophys. J. Lett. 397, L123 (1992); T. Amano, K. Hashimoto, and T. Hirao, J. Mol. Struct. 795, 190–193 (2006)G W. G. D. P. Silva, L. Bonah, P. C. Schmid, S. Schlemmer, O. Asvany, J. Chem. Phys. 160, 071101 (2024)T

The detection of cyano-group containing aromatic structures such as benzonitrile,McGuire et al. 2018, Science, 359, 202yanonaphthaleneMcGuire et al. 2021, Science, 371, 1265nd cyanoindeneSita et al. 2022 ApJL, 938, L12n interstellar clouds by radioastronomy has motivated recent laboratory investigations into their stability. Experiments at the DESIREE storage ring revealed that small polycyclic aromatic hydrocarbon cations may be more stable than previously believed, attributing this to inverse internal conversion and recurrent fluorescenceStockett et al. 2023, Nat. Comm., 14, 395 This has motivated us to obtain the electronic and vibrational spectra of these species to facilitate searches for them in other wavelength ranges. In this talk recent experiments results, obtained by action spectroscopy in a cryogenic trap, will be presented and discussed.

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McGuire et al. 2018, Science, 359, 202c McGuire et al. 2021, Science, 371, 1265a Sita et al. 2022 ApJL, 938, L12i Stockett et al. 2023, Nat. Comm., 14, 395.

We report on the ro-vibrational spectrum of C₂H₃⁺ in the CH stretching region (3125 - 3176 cm⁻¹) using leak-out-spectroscopy (LOS). P. C. Schmid et al., J. Phys. Chem. A 2022, 126, 43, 8111–8117.or the present study C₂H₃⁺ is produced in a storage ion source (SIS), mass selected, and then stored in the 22-pole ion trap, COLtrap, where it is cooled to 4 K prior to vibrational excitation by a cw IR-OPO. The LOS spectrum of mass selected and cold C₂H₃⁺ shows a rich structure which is not easy to assign. As it turns out, it contains contributions from two isomers. In one isomer, the third proton lies at the end of acetylene, HC₂H₂⁺, while in the other, that proton is in a bridged position. In addition, even at low temperatures, hot bands can lead to further spectral complexity.
In previous studies, M. W. Crofton et al., The Journal of Chemical Physics 1989, 91, 9, 5139-5153 and C. M. Gabrys et al., The Journal of Physical Chemistry 1995, 99, 42, 15611-15623.ines recorded in the same frequency range have been assigned to the ν₆ antisymmetric CH stretching band of the bridged structure. However, those spectra were much more congested and probably also contained lines from both isomers. As part of the LOS technique we are able to kick-out all ions of a specific structural and/or nuclear-spin isomer by addressing a rotational state of one of the configurations. As during this process re-population of the probing rotational state will occur, we wait long enough during kick-out to guarantee that all molecules belonging to this class leave from the trap. We will show how we can determine the respective isomeric fractions via this additional feature. In case of two isomers both with an ortho and para configuration we can determine the corresponding four fractions. By doing so the complex C₂H₃⁺ spectrum can be separated into the spectra of the respective isomers. Moreover, a direct determination of the ortho to para ratio reveals whether all three protons are equivalent in the respective isomer.

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P. C. Schmid et al., J. Phys. Chem. A 2022, 126, 43, 8111–8117.F M. W. Crofton et al., The Journal of Chemical Physics 1989, 91, 9, 5139-5153 and C. M. Gabrys et al., The Journal of Physical Chemistry 1995, 99, 42, 15611-15623.l