50 research outputs found
Photoionization in the time and frequency domain
Ultrafast processes in matter, such as the electron emission following light
absorption, can now be studied using ultrashort light pulses of attosecond
duration (s) in the extreme ultraviolet spectral range. The lack of
spectral resolution due to the use of short light pulses may raise serious
issues in the interpretation of the experimental results and the comparison
with detailed theoretical calculations. Here, we determine photoionization time
delays in neon atoms over a 40 eV energy range with an interferometric
technique combining high temporal and spectral resolution. We spectrally
disentangle direct ionization from ionization with shake up, where a second
electron is left in an excited state, thus obtaining excellent agreement with
theoretical calculations and thereby solving a puzzle raised by seven-year-old
measurements. Our experimental approach does not have conceptual limits,
allowing us to foresee, with the help of upcoming laser technology, ultra-high
resolution time-frequency studies from the visible to the x-ray range.Comment: 5 pages, 4 figure
Attosecond timing of electron emission from a molecular shape resonance
Shape resonances in physics and chemistry arise from the spatial confinement
of a particle by a potential barrier. In molecular photoionization, these
barriers prevent the electron from escaping instantaneously, so that nuclei may
move and modify the potential, thereby affecting the ionization process. By
using an attosecond two-color interferometric approach in combination with high
spectral resolution, we have captured the changes induced by the nuclear motion
on the centrifugal barrier that sustains the well-known shape resonance in
valence-ionized N. We show that despite the nuclear motion altering the
bond length by only , which leads to tiny changes in the potential
barrier, the corresponding change in the ionization time can be as large as
attoseconds. This result poses limits to the concept of instantaneous
electronic transitions in molecules, which is at the basis of the Franck-Condon
principle of molecular spectroscopy.Comment: 24 pages, 5 figure
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Time–frequency representation of autoionization dynamics in helium
Autoionization, which results from the interference between direct photoionization and photoexcitation to a discrete state decaying to the continuum by configuration interaction, is a well known example of the important role of electron correlation in light–matter interaction. Information on this process can be obtained by studying the spectral, or equivalently, temporal complex amplitude of the ionized electron wave packet. Using an energy-resolved interferometric technique, we measure the spectral amplitude and phase of autoionized wave packets emitted via the sp2+ and sp3+ resonances in helium. These measurements allow us to reconstruct the corresponding temporal profiles by Fourier transform. In addition, applying various time–frequency representations, we observe the build-up of the wave packets in the continuum, monitor the instantaneous frequencies emitted at any time and disentangle the dynamics of the direct and resonant ionization channels
Boosting cross-border regions through better cross-border transport services. The European case
Cross-border regions are the laboratories of European integration. Daily interactions across European borders let citizens experience the benefits of the European Union (EU) internal market. Still, many border barriers continue to prevent individuals and organisations from exploiting the full-potential of European border regions and the benefits of a more integrated European territory. Amongst these barriers are the absence or inappropriate supply of cross-border public transport services. In this context, this paper presents potential policy tools to increase border permeability related to cross-border public transport as well as practical results from a few case-studies implemented across Europe.info:eu-repo/semantics/publishedVersio
Plasma immunoprofiling of patients with high-risk diffuse large B-cell lymphoma : a Nordic Lymphoma Group study
Non peer reviewe
Low frequency of defective mismatch repair in a population-based series of upper urothelial carcinoma
BACKGROUND: Upper urothelial cancer (UUC), i.e. transitional cell carcinomas of the renal pelvis and the ureter, occur at an increased frequency in patients with hereditary nonpolyposis colorectal cancer (HNPCC). Defective mismatch repair (MMR) specifically characterizes HNPCC-associated tumors, but also occurs in subsets of some sporadic tumors, e.g. in gastrointestinal cancer and endometrial cancer. METHODS: We assessed the contribution of defective MMR to the development of UUC in a population-based series from the southern Swedish Cancer Registry, through microsatellite instability (MSI) analysis and immunohistochemical evaluation of expression of the MMR proteins MLH1, PMS2, MSH2, and MSH6. RESULTS: A MSI-high phenotype was identified in 9/216 (4%) successfully analyzed patients and a MSI-low phenotype in 5/216 (2%). Loss of MMR protein immunostaining was found in 11/216 (5%) tumors, and affected most commonly MSH2 and MSH6. CONCLUSION: This population-based series indicates that somatic MMR inactivation is a minor pathway in the development of UUC, but tumors that display defective MMR are, based on the immunohistochemical expression pattern, likely to be associated with HNPCC
CHEK2 1100delC in patients with metachronous cancers of the breast and the colorectum
BACKGROUND: Development of multiple primary tumors is a hallmark of hereditary cancer. At least 1/10 of breast cancers and colorectal cancers occur because of heredity and recently the cell cycle kinase 2, CHEK2 1100delC allele has been identified at a particularly high frequency in families with hereditary breast and colorectal cancer. METHODS: We utilized the Southern Sweden population-based cancer registry to identify women with double primary breast and colorectal cancer and sequenced tumor material in order to assess the contribution of the CHEK2 1100delC to the development of such metachronous tumors. RESULTS: Among the 75 patients successfully analyzed, 2 (2.5%) carried the CHEK2 1100delC allele. which was not significantly different (p = 0.26) from the 1% (3/300) carriers identified in the control group. CONCLUSION: In summary, our data suggest that the CHEK2 1100delC is not a major cause of double primary breast and colorectal cancer in Sweden, which suggests that this patient group should not routinely be screened for the CHEK2 1100delC variant