| 1. |
- Bidermane, Ieva, 1984-, et al.
(författare)
-
Characterization of Gas Phase of Iron Phthalocyanine with X-ray Photoelectron and Absorption Spectroscopies
- 2015
-
Ingår i: Physica status solidi. B, Basic research. - : Wiley. - 0370-1972 .- 1521-3951. ; 252:6, s. 1259-1265
-
Tidskriftsartikel (refereegranskat)abstract
- Despite the numerous studies dedicated to phthalocyanine molecules adsorbed on surfaces, in monolayer or thin film, very few works have been focused on the characterization of vapors of these molecules. In this article we present the C 1s, N 1s and Fe 2p photoemission results as well as N K-edge X-ray absorption data of iron phthalocyanine (FePc) in gas phase. Presented comparison of X-ray photoelectron spectroscopy and X-ray absorption spectroscopy spectra of FePc films show a great similarity with the gas phase results, confirming the molecular character of thick films. The Fe2p photoemission spectrum of the gas phase FePc, shown for the first time, can be considered as a fingerprint of the Fe(II) ionic state of the central metal of the iron phthalocyanine. The performed multiplet calculations for describing the Fe 2p XP spectrum indicate 3Eg (a1g2eg32g1) state as the most probable ground state for thick film of iron phthalocyanine.
|
|
| 2. |
- Ciavardini, Alessandra, et al.
(författare)
-
Ultra-Fast-VUV Photoemission Study of UV Excited 2-Nitrophenol
- 2019
-
Ingår i: Journal of Physical Chemistry A. - : AMER CHEMICAL SOC. - 1089-5639 .- 1520-5215. ; 123:7, s. 1295-1302
-
Tidskriftsartikel (refereegranskat)abstract
- The initial deactivation pathways of gaseous 2-nitrophenol excited at 268 nm were investigated by time-resolved photoelectron spectroscopy (TRPES) with femtosecond-VUV light, produced by a monochromatized high harmonic generation source. TRPES allowed us to obtain new, valuable experimental information about the ultrafast excited-state dynamics of 2-nitrophenol in the gas phase. In accord with recent ab initio on-the-fly nonadiabatic molecular dynamic simulations, our results validate the occurrence of an ultrafast intersystem crossing leading to an intermediate state that decays on a subpicosecond time scale with a branched mechanisms. Two decay pathways are experimentally observed. One probably involves proton transfer, leading to the most stable triplet aci-form of 2-nitrophenol; the second pathway may involve OH rotation. We propose that following intersystem crossing, an ultrafast fragmentation channel leading to OH or HONO loss could also be operative.
|
|
| 3. |
- Kivimäki, Antti, et al.
(författare)
-
Fragmentation of Methanol Molecules after Core Excitation and Core Ionization Studied by Negative-Ion/Positive-Ion Coincidence Experiments
- 2018
-
Ingår i: Journal of Physical Chemistry A. - : American Chemical Society (ACS). - 1089-5639 .- 1520-5215. ; 122:1, s. 224-233
-
Tidskriftsartikel (refereegranskat)abstract
- We have studied the fragmentation of the methanol molecule after core excitation and core ionization by observing coincidences between negative and positive ions. Five different negative ions – H-, C-, CH-, O-, and OH- – were observed at both the C 1s and O 1s edges. As negative ion formation occurs after resonant and normal Auger decay of core-hole states, it is necessarily linked with the release of positively charged fragments. Our data show that such fragmentation can happen in many different ways: We found approximately 30 negative-ion/positive-ion/positive-ion coincidence (NIPIPICO) channels. All involve only singly charged positive ions. Fragmentation channels leading to atomic ions are the most probable, but positive molecular ions are also frequently found in the context of anion formation. Coincidence yields as a function of photon energy were determined for the most intense NIPIPICO channels. Adding together the data measured at different photon energies, we could also verify the occurrence of four-ion coincidences, which involved one negative ion (H- or O-) and three positive ions.
|
|
| 4. |
- Kivimäki, Antti, et al.
(författare)
-
Yields and Time-of-Flight Spectra of Neutral High-Rydberg Fragments at the K Edges of the CO2 Molecule
- 2016
-
Ingår i: The Journal of Physical Chemistry Part A: Molecules, Spectroscopy, Kinetics, Environment and General Theory. - : American Chemical Society (ACS). - 1089-5639. ; 120:25, s. 4360-4367
-
Tidskriftsartikel (refereegranskat)abstract
- We have studied the production of neutral fragments in high-Rydberg (HR) states at the C 1s and O 1s edges of the CO2 molecule by performing two kinds of experiments. First, the yields of neutral HR fragments were measured indirectly by ionizing such fragments in a static electric field and by collecting resulting singly charged positive ions as a function of the photon energy. Such measurements reveal not only excitations below the core ionization thresholds but also thresholds for single core-hole and shakeup photoionization. Second, we obtained the mass spectra of neutral HR fragments at selected photon energies by exploiting pulsed field ionization; they show atomic fragments C(HR) and O(HR). We discuss dissociation pathways leading to the production of neutral HR fragments in core excitation and ionization of CO2.
|
|
| 5. |
- Kuusik, Ivar, et al.
(författare)
-
The electronic structure of ionic liquids based on the TFSI anion : A gas phase UPS and DFT study
- 2019
-
Ingår i: Journal of Molecular Liquids. - : Elsevier BV. - 0167-7322. ; 294
-
Tidskriftsartikel (refereegranskat)abstract
- The valence bands of [EMIM][TFSI], [DEME][TFSI] and [PYR1,4][TFSI] gas-phase ion pairs have been investigated using ultraviolet photoelectron spectroscopy (UPS). The photoelectron spectra are interpreted by using several density functional and ab initio calculation methods. Although the experimental vapor phase spectra are similar, the different calculation methods make different predictions about the HOMO molecular state of the ion-pairs of the ionic liquids. The HOMO state of the [DEME][TFSI] ion-pair is due to the TFSI anion, while in [EMIM][TFSI] it is due to the EMIM cation. However, it is difficult to make conclusive assignments for the [PYR1,4][TFSI] ionic liquid. All calculation methods predict the LUMO to be of cationic origin in all the studied ion-pairs.
|
|
| 6. |
- Pankratov, Vladimir, et al.
(författare)
-
Progress in development of a new luminescence setup at the FinEstBeAMS beamline of the MAX IV laboratory
- 2019
-
Ingår i: Radiation Measurements. - : Elsevier BV. - 1350-4487. ; 121, s. 91-98
-
Tidskriftsartikel (refereegranskat)abstract
- FinEstBeAMS is a new materials science beamline at the 1.5 GeV storage ring of the MAX IV Laboratory in Lund, Sweden. It has been built based on grazing incidence monochromatization of synchrotron light, which allows to cover a remarkably wide excitation energy range from ultraviolet to soft x-rays (4.5–1450 eV). A new mobile luminescence spectroscopy end station has been commissioned with design benefitting from the advantages of a high flux elliptically polarizing undulator light source. We report on the design of the luminescence end station, its technical realization and performance achieved so far. Special attention is paid to the experimental challenges for luminescence spectroscopy under grazing incidence excitation conditions. The first luminescence results obtained demonstrate a reliable performance of the advanced setup at FinEstBeAMS.
|
|
| 7. |
- Stråhlman, Christian, et al.
(författare)
-
A Tandem Time--of--Flight Spectrometer for Negative--Ion/Positive--Ion Coincidence Measurements with Soft X-ray Excitation
- 2016
-
Ingår i: Review of Scientific Instruments. - : AIP Publishing. - 1089-7623 .- 0034-6748. ; 87:1
-
Tidskriftsartikel (refereegranskat)abstract
- We present a newly constructed spectrometer for negative--ion/positive--ion coincidence spectroscopy of gaseous samples. The instrument consists of two time--of--flight ion spectrometers and a magnetic momentum filter for deflection of electrons. The instrument can measure double and triple coincidences between mass--resolved negative and positive ions with high detection efficiency. First results include identification of several negative--ion/positive--ion coincidence channels following inner-shell photoexcitation of sulfur hexaflouride (SF$_6$).
|
|
| 8. |
- Stråhlman, Christian, et al.
(författare)
-
Negative- and positive-ion fragmentation of core-excited formic-acid molecules studied with three- and four-ion coincidence spectroscopy
- 2017
-
Ingår i: Physical Review A: covering atomic, molecular, and optical physics and quantum information. - : American Physical Society. - 2469-9926 .- 2469-9934. ; 96:2
-
Tidskriftsartikel (refereegranskat)abstract
- The negative-ion fragmentation of formic acid (HCOOH) is studied with negative- and positive-ion coincidence spectroscopy. We report four-body ionic fragmentation where up to three positive ions are collected in coincidence with one negative ion. We report yields for 21 three-body channels and five four-body channels. More than 80% of all negative-ion fragmentation involves production of O-, and it is dominated by complete dissociation of all molecular bonds. Negative-ion creation is most abundant at high-Rydberg resonances and just above the molecule's core-ionization potentials. The existence of four-body fragmentation channels evidences a strong charge redistribution in the molecule.
|
|
| 9. |
|
|
| 10. |
- Stråhlman, Christian, et al.
(författare)
-
Negative-Ion/Positive-Ion Coincidence Yields of Core-Excited Water
- 2016
-
Ingår i: The Journal of Physical Chemistry Part A: Molecules, Spectroscopy, Kinetics, Environment and General Theory. - : American Chemical Society (ACS). - 1520-5215. ; 120:32, s. 6389-6393
-
Tidskriftsartikel (refereegranskat)abstract
- We report yields of mass-resolved negative ions and positive ions measured in coincidence after core-excitation of water molecules. The analysis of negative-ion/positive-ion and negative-ion/positive-ion/positive-ion coincidence events provides new information on pathways leading to negative ion production, enhancing the present understanding of the dissociation processes of the water molecule. Dissociation following (resonant) Auger decay dominates negative ion production, but radiative decay is shown to contribute above the O 1s ionization threshold. A peak in the H-/O+ yield above the O 1s threshold is attributed to decay from doubly excited states.
|
|
