| 1. |
- Beye, Martin, et al.
(författare)
-
Chemical Bond Activation Observed with an X-ray Laser
- 2016
-
Ingår i: Journal of Physical Chemistry Letters. - : American Chemical Society (ACS). - 1948-7185 .- 1948-7185. ; 7:18, s. 3647-3651
-
Tidskriftsartikel (refereegranskat)abstract
- The concept of bonding and antibonding orbitals is fundamental in chemistry. The population of those orbitals and the energetic difference between the two reflect the strength of the bonding interaction. Weakening the bond is expected to reduce this energetic splitting, but the transient character of bond-activation has so far prohibited direct experimental access. Here we apply time-resolved soft X-ray spectroscopy at a free electron laser to directly observe the decreased bonding antibonding splitting following bond-activation using an ultrashort optical laser pulse.
|
|
| 2. |
- Beye, M., et al.
(författare)
-
Selective Ultrafast Probing of Transient Hot Chemisorbed and Precursor States of CO on Ru(0001)
- 2013
-
Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 110:18
-
Tidskriftsartikel (refereegranskat)abstract
- We have studied the femtosecond dynamics following optical laser excitation of CO adsorbed on a Ru surface by monitoring changes in the occupied and unoccupied electronic structure using ultrafast soft x-ray absorption and emission. We recently reported [M. Dell'Angela et al. Science 339, 1302 (2013)] a phonon-mediated transition into a weakly adsorbed precursor state occurring on a time scale of >2 ps prior to desorption. Here we focus on processes within the first picosecond after laser excitation and show that the metal-adsorbate coordination is initially increased due to hot-electron-driven vibrational excitations. This process is faster than, but occurs in parallel with, the transition into the precursor state. With resonant x-ray emission spectroscopy, we probe each of these states selectively and determine the respective transient populations depending on optical laser fluence. Ab initio molecular dynamics simulations of CO adsorbed on Ru(0001) were performed at 1500 and 3000 K providing insight into the desorption process.
|
|
| 3. |
- Dell'Angela, M., et al.
(författare)
-
Real-Time Observation of Surface Bond Breaking with an X-ray Laser
- 2013
-
Ingår i: Science. - : American Association for the Advancement of Science (AAAS). - 0036-8075 .- 1095-9203. ; 339:6125, s. 1302-1305
-
Tidskriftsartikel (refereegranskat)abstract
- We used the Linac Coherent Light Source free-electron x-ray laser to probe the electronic structure of CO molecules as their chemisorption state on Ru(0001) changes upon exciting the substrate by using a femtosecond optical laser pulse. We observed electronic structure changes that are consistent with a weakening of the CO interaction with the substrate but without notable desorption. A large fraction of the molecules (30%) was trapped in a transient precursor state that would precede desorption. We calculated the free energy of the molecule as a function of the desorption reaction coordinate using density functional theory, including van der Waals interactions. Two distinct adsorption wells-chemisorbed and precursor state separated by an entropy barrier-explain the anomalously high prefactors often observed in desorption of molecules from metals.
|
|
| 4. |
- Engdahl, Jenny, et al.
(författare)
-
Effects of surgical specialization and surgeon resection volume on postoperative complications and mortality rate after emergent colon cancer resection
- 2023
-
Ingår i: BJS Open. - 2474-9842. ; 7:3
-
Tidskriftsartikel (refereegranskat)abstract
- Background: The aim of this study was to evaluate the effect of surgical specialization and surgeon resection volume on short-term outcome after emergent colon cancer resections. Methods: A retrospective analysis of all patients who underwent resections for colon cancer between 2011 and 2020 at Helsingborg Hospital, Sweden was performed. The senior surgeon participating in each procedure was classified as a colorectal surgeon or a non-colorectal surgeon. Non-colorectal surgeons were further divided into acute care surgeons or surgeons with other specialties. Surgeons were also divided into three groups based on median yearly resection volumes. Postoperative complications and 30- or 90-day mortality rate after emergent colon cancer resections were compared in patients operated on by surgeons with different specializations and yearly resection volumes. Results: Of 1121 patients resected for colon cancer, 235 (21.0 per cent) had emergent procedures. The complication rate of emergent resections was similar in patients operated on by colorectal surgeons and non-colorectal surgeons (54.1 versus 51.1 per cent respectively), and the subgroup of acute care surgeons (45.8 per cent), whereas resections performed by general surgeons were significantly associated with more frequent complications (odds ratio (OR) 2.5 (95 per cent c.i. 1.1 to 6.1)). The complication rate was numerically highest in patients operated on by surgeons with the highest resection volumes, which differed significantly from that of surgeons with intermediate resection volumes (OR 4.2 (95 per cent c.i. 1.1 to 16.0)). There was no difference in the mortality rate of patients operated on by surgeons with different specializations or yearly resection volumes. Conclusion: This study documented similar morbidity and mortality rates after emergent colon resection performed by colorectal and acute care surgeons, but patients operated on by general surgeons had more frequent complications.
|
|
| 5. |
- Engdahl, Jenny, et al.
(författare)
-
Short- and long-term outcome after colon cancer resections performed by male and female surgeons : A single-center retrospective cohort study
-
Ingår i: Scandinavian Journal of Surgery. - 1457-4969.
-
Tidskriftsartikel (refereegranskat)abstract
- Background and objective: To assess the effect of surgeon sex on short- and long-term outcomes after colon cancer resections. Methods: Clinical data of patients who underwent colon cancer resections between 2010 and 2020 at Helsingborg Hospital, Sweden, were retrospectively obtained from medical records. The sex of the surgeon of each procedure was recorded. Morbidity, mortality, and long-term survival were compared in patients operated by male and female surgeons. Results: Colon cancer resections were performed by 23 male and 9 female surgeons in 1113 patients (79% elective, 21% emergent). After elective surgery, there was no difference in postoperative complications, 30-day mortality, or long-term survival between patients operated by male and female surgeons. Following emergent resections, the complication rate was significantly lower in patients operated by female surgeons (41.3% vs 58.1%, p = 0.019). Similarly, the rates of R1-resections (0% vs 5.2%, p = 0.039), reoperations (3.8% vs 14.2%, p = 0.014), and intensive care unit (ICU) care (6.3% vs 17.4%, p = 0.018) were significantly lower for patients operated by female surgeons, but there was no difference in 30-day mortality (6.3% vs 5.2%, p = 0.767). Cox regression analysis showed that long-term and cancer-free survival in patients emergently operated by male surgeons was significantly shorter than that of patients operated by female surgeons (hazard ratio = 1.9 (95% confidence interval (CI) = 1.3–2.8), p = 0.001 and hazard ratio = 1.7 (95% CI = 1.1–2.7), p = 0.016). Conclusions: The short- and long-term outcome after elective colon cancer resections were similar in patients operated by male and female surgeons. The outcome following emergent resections performed by female surgeons compared favorably with that of male surgeons, with fewer complications and reoperations and better long-term survival.
|
|
| 6. |
- Gladh, Jörgen, et al.
(författare)
-
Detection of adsorbate overlayer structural transitions using sum-frequency generation spectroscopy
- 2015
-
Ingår i: Surface Science. - : Elsevier BV. - 0039-6028 .- 1879-2758. ; 633, s. 77-81
-
Tidskriftsartikel (refereegranskat)abstract
- We demonstrate that temperature-programmed vibrational sum-frequency generation (SFG) spectroscopy has a unique sensitivity to certain adsorbate overlayer structural transitions. In the CO stretching vibration of co-adsorbed CO/O(2x1)/Ru(0001) we observe pronounced dips in the spectral intensity as the adsorbate overlayer undergoes structural transitions with temperature. Combining with temperature-programmed desorption (TPD) a more complete picture of temperature-dependent structural transitions is obtained. We extract kinetic parameters from the SFG data and obtain good agreement with TPD when both techniques see the same transition. Infrared-infrared visible SFG is used to determine changes in inter-adsorbate coupling that allow us to experimentally assign the structural transitions. Furthermore, density functional theory calculations of the proposed structures and energetics are performed to verify the experimental assignments.
|
|
| 7. |
- Gladh, Jörgen, et al.
(författare)
-
X-ray emission spectroscopy and density functional study of CO/Fe(100)
- 2012
-
Ingår i: Journal of Chemical Physics. - : AIP Publishing. - 0021-9606 .- 1089-7690. ; 136:3
-
Tidskriftsartikel (refereegranskat)abstract
- We report x-ray emission and absorption spectroscopy studies of the electronic structure of the pre-dissociative alpha(3) phase of CO bound at hollow sites of Fe(100) as well as of the on-top bound species in the high-coverage alpha(1) phase. The analysis is supported by density functional calculations of structures and spectra. The bonding of lying down CO in the hollow site is well described in terms of pi to pi* charge transfer made possible through bonding interaction also at the oxygen in the minority spin-channel. The on-top CO in the mixed, high-coverage alpha(1) phase is found to be tilted due to adsorbate-adsorbate interaction, but still with bonding mainly characteristic of vertical on-top adsorbed CO similar to other transition-metal surfaces.
|
|
| 8. |
- Nilsson, Anders, et al.
(författare)
-
Catalysis in real time using X-ray lasers
- 2017
-
Ingår i: Chemical Physics Letters. - : Elsevier BV. - 0009-2614 .- 1873-4448. ; 675, s. 145-173
-
Tidskriftsartikel (refereegranskat)abstract
- We describe how the unique temporal and spectral characteristics of X-ray free-electron lasers (XFEL) can be utilized to follow chemical transformations in heterogeneous catalysis in real time. We highlight the systematic study of CO oxidation on Ru(0001), which we initiate either using a femtosecond pulse from an optical laser or by activating only the oxygen atoms using a THz pulse. We find that CO is promoted into an entropy-controlled precursor state prior to desorbing when the surface is heated in the absence of oxygen, whereas in the presence of oxygen, CO desorbs directly into the gas phase. We monitor the activation of atomic oxygen explicitly by the reduced split between bonding and antibonding orbitals as the oxygen comes out of the strongly bound hollow position. Applying these novel XFEL techniques to the full oxidation reaction resulted in the surprising observation of a significant fraction of the reactants at the transition state through the electronic signature of the new bond formation.
|
|
| 9. |
|
|
| 10. |
- Xin, H., et al.
(författare)
-
Strong Influence of Coadsorbate Interaction on CO Desorption Dynamics on Ru(0001) Probed by Ultrafast X-Ray Spectroscopy and Ab Initio Simulations
- 2015
-
Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 114:15
-
Tidskriftsartikel (refereegranskat)abstract
- We show that coadsorbed oxygen atoms have a dramatic influence on the CO desorption dynamics from Ru(0001). In contrast to the precursor-mediated desorption mechanism on Ru(0001), the presence of surface oxygen modifies the electronic structure of Ru atoms such that CO desorption occurs predominantly via the direct pathway. This phenomenon is directly observed in an ultrafast pump-probe experiment using a soft x-ray free-electron laser to monitor the dynamic evolution of the valence electronic structure of the surface species. This is supported with the potential of mean force along the CO desorption path obtained from density-functional theory calculations. Charge density distribution and frozen-orbital analysis suggest that the oxygen-induced reduction of the Pauli repulsion, and consequent increase of the dative interaction between the CO 5 sigma and the charged Ru atom, is the electronic origin of the distinct desorption dynamics. Ab initio molecular dynamics simulations of CO desorption from Ru(0001) and oxygen-coadsorbed Ru(0001) provide further insights into the surface bond-breaking process.
|
|
