| 1. |
- Andersson, Åke, et al.
(författare)
-
IRMPD Spectroscopy of Homo- and Heterochiral Asparagine Proton-Bound Dimers in the Gas Phase
- 2021
-
Ingår i: Journal of Physical Chemistry A. - : American Chemical Society (ACS). - 1089-5639 .- 1520-5215. ; 125:34, s. 7449-7456
-
Tidskriftsartikel (refereegranskat)abstract
- We investigate gas-phase structures of homo- and heterochiral asparagine proton-bound dimers with infrared multi-photon dissociation (IRMPD) spectroscopy and quantum-chemical calculations. Their IRMPD spectra are recorded at room temperature in the range of 500-1875 and 3000-3600 cm(-1). Both varieties of asparagine dimers are found to be charge-solvated based on their IRMPD spectra. The location of the principal intramolecular H-bond is discussed in light of harmonic frequency analyses using the B3LYP functional with GD3BJ empirical dispersion. Contrary to theoretical analyses, the two spectra are very similar.
|
|
| 2. |
- Andersson, Åke, et al.
(författare)
-
Structure of Proton-Bound Methionine and Tryptophan Dimers in the Gas Phase Investigated with IRMPD Spectroscopy and Quantum Chemical Calculations
- 2020
-
Ingår i: Journal of Physical Chemistry A. - : American Chemical Society (ACS). - 1089-5639 .- 1520-5215. ; 124:12, s. 2408-2415
-
Tidskriftsartikel (refereegranskat)abstract
- The structures of three proton-bound dimers (Met(2)H(+), MetTrpH(+), and Trp(2)H(+)) are investigated in the gas phase with infrared multiple photon disassociation (IRMPD) spectroscopy in combination with quantum chemical calculations. Their IRMPD spectra in the range of 600-1850 cm(-1) are obtained experimentally using an FT-ICR mass spectrometer and the CLIO free electron laser as an IR light source. The most abundant conformers are elucidated by comparing the IRMPD spectra with harmonic frequencies obtained at the B3LYPGD3BJ/6-311++G** level of theory. Discrepancies between the experimental and theoretical data in the region of 1500-1700 cm(-1) are attributed to the anharmonicity of the amino bending modes. We confirm the result of a previous IRMPD study that the structure of gas-phase Trp(2)H(+) is charge-solvated but find that there are more stable structures than originally reported (Feng, R.; Yin, H.; Kong, X. Rapid Commun. Mass Spectrom. 2016, 30, 24-28). In addition, gas-phase Met(2)H(+) and MetTrpH(+) have been revealed to have charge-solvated structures. For all three dimers, the most stable conformer is found to be of type A. The spectrum of Met(2)H(+), however, cannot be explained without some abundance of type B charge-solvated conformers as well as salt-bridged structures.
|
|
| 3. |
- Bogot, Alon, et al.
(författare)
-
The mutual neutralization of hydronium and hydroxide
- 2024
-
Ingår i: Science. - 0036-8075 .- 1095-9203. ; 383:6680, s. 285-289
-
Tidskriftsartikel (refereegranskat)abstract
- Mutual neutralization of hydronium (H3O+) and hydroxide (OH−) ions is a very fundamental chemical reaction. Yet, there is only limited experimental evidence about the underlying reaction mechanisms. Here, we report three-dimensional imaging of coincident neutral products of mutual-neutralization reactions at low collision energies of cold and isolated ions in the cryogenic double electrostatic ion-beam storage ring (DESIREE). We identified predominant H2O + OH + H and 2OH + H2 product channels and attributed them to an electron-transfer mechanism, whereas a minor contribution of H2O + H2O with high internal excitation was attributed to proton transfer. The reported mechanism-resolved internal product excitation, as well as collision-energy and initial ion-temperature dependence, provide a benchmark for modeling charge-transfer mechanisms.
|
|
| 4. |
- Poline, Mathias, et al.
(författare)
-
Final-state-resolved mutual neutralization in I+ - I− collisions
- 2022
-
Ingår i: Physical Review A: covering atomic, molecular, and optical physics and quantum information. - : American Physical Society (APS). - 2469-9926 .- 2469-9934. ; 106:1
-
Tidskriftsartikel (refereegranskat)abstract
- We have studied the mutual neutralization reaction of atomic iodine ions (i.e., I++I−→I+I) in a cryogenic double electrostatic ion-beam storage-ring apparatus. Our results show that the reaction forms iodine atoms either in the ground-state configuration (I(5p52P∘), ∼40%) or with one atom in an electronically excited state (I(6s2[2]), ∼60%), with no significant variation over the branching ratios in the studied collision-energy range (0.1–0.8 eV). We estimate the total charge-transfer cross section to be of the order of 10−13cm2 at 0.1 eV collision energy. Ab initio relativistic electronic structure calculations of the potential-energy curves of I2 suggest that the reaction takes place at short internuclear distances. The results are discussed in view of their importance for applications in electric thrusters.
|
|
| 5. |
- Poline, Mathias, et al.
(författare)
-
Mutual neutralisation of O+ with O− : investigation of the role of metastable ions in a combined experimental and theoretical study
- 2021
-
Ingår i: Physical Chemistry, Chemical Physics - PCCP. - : Royal Society of Chemistry (RSC). - 1463-9076 .- 1463-9084. ; 23:43, s. 24607-24616
-
Tidskriftsartikel (refereegranskat)abstract
- The mutual neutralisation of O+ with O− has been studied in a double ion-beam storage ring with combined merged-beams, imaging and timing techniques. Branching ratios were measured at the collision energies of 55, 75 and 170 (± 15) meV, and found to be in good agreement with previous single-pass merged-beams experimental results at 7 meV collision energy. Several previously unidentified spectral features were found to correspond to mutual neutralisation channels of the first metastable state of the cation (O+(2Do), τ ≈ 3.6 hours), while no contributions from the second metastable state (O+(2Po), τ ≈ 5 seconds) were observed. Theoretical calculations were performed using the multi-channel Landau–Zener model combined with the anion centered asymptotic method, and gave good agreement with several experimentally observed channels, but could not describe well observed contributions from the O+(2Do) metastable state as well as channels involving the O(3s 5So) state.
|
|
| 6. |
- Poline, Mathias
(författare)
-
Mutual neutralisation reactions in atmospheric and industrial plasmas
- 2022
-
Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis deals with experimental studies of electron transfer reactions between oppositely charged ions (mutual neutralisation). These were performed at the unique double electrostatic ion storage ring DESIREE at Stockholm University, which was put into full operation in 2017. In the first two published articles of this thesis, two atmospheric collision systems are treated, namely O+/O− and N+/O−. The aim was to reproduce previous published results from a single-pass (non-stored) merged ion beams setup in UCLouvain (Belgium) and thus provide a measure of DESIREE’s capacity and resolution. In addition, the effects of metastable ions were investigated with the support of theoretical calculations. The third published paper of this thesis deals with collisions between I+ and I− (iodine ions), a process relevant to electric thrusters for new spacecraft. The results are compared with theoretical calculations in order to provide an understanding of how the reaction takes place. Preliminary results on electron transfer reactions between diatomic molecules and atoms are presented.
|
|
| 7. |
- Poline, Mathias, et al.
(författare)
-
Mutual Neutralization of NO plus with O-
- 2024
-
Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 132:2
-
Forskningsöversikt (refereegranskat)abstract
- We have studied the mutual neutralization reaction of vibronically cold NO+ with O- at a collision energy of approximate to 0.1 eV and under single-collision conditions. The reaction is completely dominated by production of three ground-state atomic fragments. We employ product-momentum analysis in the framework of a simple model, which assumes the anion acts only as an electron donor and the product neutral molecule acts as a free rotor, to conclude that the process occurs in a two-step mechanism via an intermediate Rydberg state of NO which subsequently fragments.
|
|
| 8. |
- Poline, Mathias, et al.
(författare)
-
Storage-ring study of the mutual neutralization of N plus with O minus
- 2022
-
Ingår i: Physical Review A: covering atomic, molecular, and optical physics and quantum information. - : American Physical Society. - 2469-9926 .- 2469-9934. ; 105:6
-
Tidskriftsartikel (refereegranskat)abstract
- The double ion storage ring DESIREE has been used in combination with position- and time-sensitive detectors to study the mutual neutralization of N+ with O- at 40 meV collision energy. Several previously unassigned spectral features observed in a recent single-pass merged-beams experiment at 7 meV collision energy [Phys. Rev. Lett. 121, 083401 (2018)], were also observed in the present experiment. It was found that neutralization channels of the first metastable state of the cation [N+(1D), τ≈ 256 s] could explain the majority of these features, while the second metastable state [N+(1S), τ≈ 0.9 s] was not found to contribute significantly. The branching ratios into the different electronically excited states of N were determined and found to be in good agreement between the two experiments. Theoretical calculations using the multichannel Landau-Zener model were found to yield good results for a number of channels, but could not describe some observed contributions, possibly due to the presence of other processes not accounted for in the model.
|
|
| 9. |
- Poline, Mathias, et al.
(författare)
-
Storage-ring study of the mutual neutralization of N+ with O−
- 2022
-
Ingår i: Physical Review A: covering atomic, molecular, and optical physics and quantum information. - : American Physical Society (APS). - 2469-9926 .- 2469-9934. ; 105:6
-
Tidskriftsartikel (refereegranskat)abstract
- The double ion storage ring DESIREE has been used in combination with position- and time-sensitive detectors to study the mutual neutralization of N+ with O− at 40 meV collision energy. Several previously unassigned spectral features observed in a recent single-pass merged-beams experiment at 7 meV collision energy [Phys. Rev. Lett. 121, 083401 (2018)], were also observed in the present experiment. It was found that neutralization channels of the first metastable state of the cation [N+(1D),τ≈256s] could explain the majority of these features, while the second metastable state [N+(1S),τ≈0.9s] was not found to contribute significantly. The branching ratios into the different electronically excited states of N were determined and found to be in good agreement between the two experiments. Theoretical calculations using the multichannel Landau-Zener model were found to yield good results for a number of channels, but could not describe some observed contributions, possibly due to the presence of other processes not accounted for in the model.
|
|
| 10. |
- Poline, Mathias, et al.
(författare)
-
Theoretical studies of infrared signatures of proton‐bound amino acid dimers with homochiral and heterochiral moieties
- 2020
-
Ingår i: Chirality. - : Wiley. - 0899-0042 .- 1520-636X. ; 32:3, s. 359-369
-
Tidskriftsartikel (refereegranskat)abstract
- Proton‐bound homochiral and heterochiral dimers, X‐H+‐X, of five amino acids (X = Ser, Ala, Thr, Phe, and Arg) are investigated theoretically using quantum chemical density functional theory (DFT) calculations and molecular dynamics simulations with the aim to unveil diastereomer‐specific mid‐infrared (mid‐IR) absorption bands in the spectral range of 1000 to 1800 cm−1. The theoretical calculations performed in this work imply that all systems, except Ala2H+, have distinct mid‐IR absorption bands in homochiral and heterochiral configurations, which make them appropriate systems to be studied experimentally with mid‐IR spectroscopy. We show that intermolecular interaction with the side chain, in the form of hydrogen bonding or cation‐π interaction, is necessary for chiral effects to be present in the mid‐IR spectra of proton‐bound dimers of amino acids. We also report new conformers for Ala2H+, Thr2H+, Phe2H+, and Arg2H+, which were not found in earlier studies of these dimers.
|
|
