Search

Two fundamental halocarbon ions, CH2Cl+ and CH3ClH+, were studied in the gas phase using the FELion 22-pole ion trap apparatus and the Free Electron Laser for Infrared eXperiments (FELIX) at Radboud University, Nijmegen (the Netherlands). The vibrational bands of a total of four isotopologs, CH235,37Cl+ and CH335,37ClH+, were observed in selected wavenumber regions between 500 and 2900 cm−1 and then spectroscopically assigned based on the results of anharmonic force field calculations performed at the CCSD(T) level of theory. As the infrared photodissociation spectroscopy scheme employed probes singly Ne-tagged weakly bound complexes, complementary quantum-chemical calculations of selected species were also performed. The impact of tagging on the vibrational spectra of CH2Cl+ and CH3ClH+ is found to be virtually negligible for most bands; for CH3ClH+–Ne, the observations suggest a proton-bound structural arrangement. The experimental band positions as well as the best estimate rotational molecular parameters given in this work provide a solid basis for future spectroscopic studies at high spectral resolutions. [ABSTRACT FROM AUTHOR]

The carbon chain ions HC 3 O + and HC 3 S + – longer variants of the famous 'X-ogen' line carrier HCO + – have been observed for the first time using two cryogenic 22-pole ion trap apparatus (FELion, Coltrap) and two different light sources: the Free Electron Laser for Infrared eXperiments (FELIX), which was operated between 460 and 2500 cm − 1 , and an optical parametric oscillator operating near 3200 cm − 1 ; signals from both experiments were detected by infrared predissociation action spectroscopy. The majority of vibrational fundamentals were observed for both ions and their wavenumbers compare very favourably with results from high-level anharmonic force field calculations performed here at the coupled-cluster singles and doubles level augmented by a perturbative treatment of triple excitations, CCSD(T). As the action scheme employed here probes the Ne-tagged weakly bound variants, Ne–HC 3 O + and Ne–HC 3 S + , corresponding calculations of these systems were also performed. Differences in the structures and molecular force fields between the bare ions and their Ne-tagged complexes are found to be very small. [ABSTRACT FROM AUTHOR]

The carbon chain ions HC 3 O + and HC 3 S + – longer variants of the famous 'X-ogen' line carrier HCO + – have been observed for the first time using two cryogenic 22-pole ion trap apparatus (FELion, Coltrap) and two different light sources: the Free Electron Laser for Infrared eXperiments (FELIX), which was operated between 460 and 2500 cm − 1 , and an optical parametric oscillator operating near 3200 cm − 1 ; signals from both experiments were detected by infrared predissociation action spectroscopy. The majority of vibrational fundamentals were observed for both ions and their wavenumbers compare very favourably with results from high-level anharmonic force field calculations performed here at the coupled-cluster singles and doubles level augmented by a perturbative treatment of triple excitations, CCSD(T). As the action scheme employed here probes the Ne-tagged weakly bound variants, Ne–HC 3 O + and Ne–HC 3 S + , corresponding calculations of these systems were also performed. Differences in the structures and molecular force fields between the bare ions and their Ne-tagged complexes are found to be very small. [ABSTRACT FROM AUTHOR]

Infrared action spectra of the protonated forms of two fundamental organic nitriles, vinyl cyanide, C2H3CN , and ethyl cyanide, C2H5CN , have been observed using the FELion 22-pole ion trap apparatus and the Free Electron Laser for Infrared eXperiments (FELIX) at Radboud University, Nijmegen (The Netherlands). Vibrational bands of both ions were observed in the wavenumber regime between 300 and 2500 cm−1 and spectroscopically assigned based on results from anharmonic force field calculations performed here at the coupled cluster level of theory. As the action spectroscopy scheme used in the present study probes the Ne-tagged weakly bound complexes, C 2 H 3 CNH + − Ne and C 2 H 5 CNH + − Ne, corresponding quantum-chemical calculations of these systems were also performed. Significant blueshifts observed for the strong -CNH + bending modes indicate that the neon atom is attached to the proton bound to the nitrile group in both molecular ions. [Display omitted] • First infrared spectroscopic study of protonated vinyl- and ethyl cyanide. • Free Electron Laser for Infrared eXperiments, FELIX, used as radiation source. • Detection via infrared photodissociation of the Ne-ion clusters. • Experimental study complemented by high-level CCSD(T) calculations. [ABSTRACT FROM AUTHOR]

The low-lying rotational states ( J = 0, … , 5) of CD 2 H + have been probed by high-resolution ro-vibrational and pure rotational spectroscopy, applying several action spectroscopic methods in a cryogenic 22-pole ion trap. For this, the ν 1 ro-vibrational band has been revisited, detecting 108 transitions, among which 36 are new. The use of a frequency comb system allowed us to measure the ro-vibrational transitions with high precision and accuracy, typically better than 1 MHz. The high precision has been confirmed by comparing equal combination differences in the ground and excited state. Moreover, precise predictions of pure rotational transitions were possible for the ground state. Twenty-five rotational transitions have been detected directly by a novel IR-mm-wave double resonance method, giving rise to highly accurate ground state spectroscopic parameters. [ABSTRACT FROM AUTHOR]

[Display omitted] • Cryogenic action spectroscopy is applied to protonated methyl cyanide, CH 3 CNH+, a potential interstellar molecule. • Broad-range vibrational gas-phase spectra are recorded with FELIX. • The extracted vibrational band positions allow to benchmark quantum-chemical calculations. • Discussion on the influence of rare-gas tagging on the vibrational band positions. • Prediction of rotational spectroscopic constants for low-lying vibrational states. The gas phase vibrational spectrum of CH 3 CNH+ is investigated using a messenger infrared predissociation (IRPD) action spectroscopic method. Vibrational bands were recorded in the 300-1700 cm−1 and 2000-3300 cm−1 regions making use of the widely tunable free electron laser for infrared experiments, FELIX, coupled to a cryogenic ion trap instrument. Band assignments were aided by high-level quantum-chemical calculations, which showed excellent agreement with the experimental data. Effects of the neon atom used as messenger in the IRPD method are investigated in detail. The data presented here will support astronomical searches for the CH 3 CNH+ ion in space, and provide a basis for high-resolution ro-vibrational and pure rotational studies in vibrationally excited states. [ABSTRACT FROM AUTHOR]

• Cryogenic action spectroscopy is applied to astrochemical relevant hydrocarbon ions. • Broadband vibrational gas-phase spectra of the propargyl and cyclopropenium cations are recorded with FELIX. • First spectroscopic characterization of their perdeuterated variants. • The extracted vibrational band positions allow to benchmark quantum-chemical calculations. • Isomer-selective formation pathways are investigated. Gas phase vibrational spectra of [C 3 H 3 ]+ isomers and their fully deuterated isotopologues measured in a cryogenic 22-pole ion trap are presented. The widely tunable free electron laser for infrared experiments, FELIX, was employed to cover the frequency range 500–2400 cm−1, complemented with an OPO/OPA system covering 2800–3400 cm−1. Spectral assignments for both the linear and cyclic isomeric form (H 2 C 3 H+ and c-C 3 H 3 +, respectively) are made based on various high-level computational studies. The effect of ion source conditions and different precursors (allene and propargyl chloride) for the preferential production of a specific isomer is discussed. The perturbation of the vibrational band position due to complexation with neon in the recorded infrared-predissociation (IRPD) spectra are also reported in this study. [ABSTRACT FROM AUTHOR]

The carbon-rich molecular ions C 3 H＋ and HC 3 O＋ have been studied for the first time at high spectral resolution in the 5 μ m wavelength regime employing leak-out spectroscopy of their ν 2 (C 3 H＋) and ν 3 (HC 3 O＋) vibrational fundamentals. All measurements were performed in a newly built cryogenic 22-pole ion trap apparatus, the COLtrap II instrument. Besides the action spectroscopic characterization the new measurements have also been used towards optimization and an improved understanding of the leak-out process via a semi-quantitative kinetics model for which some rates are determined or estimated and rationalized. [Display omitted] • First rotationally resolved spectra of C 3 H＋ and HC 3 O＋ ions in the C-C stretching range. • Leak-out spectra measured in the new ion trap spectrometer COLtrap II. • Systematic studies optimizing the signal of leak-out spectroscopy • Kinetics model rationalizing the steps involved in the leak-out process [ABSTRACT FROM AUTHOR]

[Display omitted] • Stable EI-MS molecular ions of Phenol and Aniline are the ground state structures. • Phenol and Aniline tautomers are not accessible with cryogenic ion trapping. • Phenol and Aniline deliver both cyclopentadiene [C 5 H 6 ] + radical cations. Molecular ions of phenol and aniline as well as the fragment ion at m / z 66 formed by electron ionization are examined with cryogenic messenger-IR ion spectroscopy and theory. According to the recorded IR spectra aromatic ground state molecular ions of phenol and aniline are clearly identified. Similar to earlier reports our new set of spectroscopic and computational results supports the assumption that tautomeric molecular ions of phenol and aniline are only short-lived intermediates in the reaction path to the ultimate CO loss reaction product of phenol as well as the HNC loss product of aniline. Even the present cryogenic messenger-IR ion spectroscopy approach failed to collect spectroscopic evidence of the intermediate presence of these elusive tautomers of phenol and aniline molecular ions. However, our study clearly shows that the electron ionization mass spectrometry dissociation product ion of phenol and aniline at m / z 66 is the cyclopentadiene radical cation [C 5 H 6 ] + for the presence of which convincing spectroscopic evidence could be collected proving the structure assignment and identification. All messenger-IR ion spectroscopy experiments were conducted on a cryogenic 22-pole ion trap with the use of neon atoms for tagging. The MS instrument was coupled to a free electron laser delivering wavelength tunable IR radiation for spectroscopy. Harmonic and anharmonic force field calculations complement the experiments and support band assignments of the recorded IR spectra and general data interpretation. [ABSTRACT FROM AUTHOR]

[Display omitted] • The 22-pole trap machine COLTRAP investigates NO+ ions at low temperature. • The three lowest rotational transitions of 14NO+ are recorded. • The quadrupole hyperfine structure from the presence of the nitrogen nucleus is resolved. • The spectroscopic parameters are considerably improved. The pure rotational spectrum of the 14NO+ cation has been revisited and its fundamental transition measured for the first time. Using a cryogenic ion trap apparatus and applying an action spectroscopy scheme, the transitions J ′ ← J ″ = 1 ← 0 through J ′ ← J ″ = 3 ← 2 have been detected, exhibiting well-resolved hyperfine structure from the presence of the 14N nucleus. Compared to former investigations, the spectroscopic constants are considerably improved and the nuclear spin - rotation interaction constant determined for the first time. [ABSTRACT FROM AUTHOR]

• First high-resolution infrared study of CN+. • Study of two isotopic species, C14N+ and C15N+. • Derivation of an isotopically invariant fit. • First observation of the CN+ + H 2 reaction at cryogenic temperatures. Rotational-vibrational transitions of the fundamental vibrational modes of the 12 C 14 N+ and 12 C 15 N+ cations have been observed for the first time using a cryogenic ion trap apparatus with an action spectroscopy scheme. The lines P (3) to R (3) of 12 C 14 N+ and R (1) to R (3) of 12 C 15 N+ have been measured, limited by the trap temperature of approximately 4 K and the restricted tuning range of the infrared laser. Spectroscopic parameters are presented for both isotopologues, with band origins at 2000.7587(1) and 1970.321(1) cm−1, respectively, as well as an isotope independent fit combining the new and the literature data. [ABSTRACT FROM AUTHOR]