338 research outputs found
Probing single-photon ionization on the attosecond time scale
We study photoionization of argon atoms excited by attosecond pulses using an
interferometric measurement technique. We measure the difference in time delays
between electrons emitted from the and from the shell, at
different excitation energies ranging from 32 to 42 eV. The determination of
single photoemission time delays requires to take into account the measurement
process, involving the interaction with a probing infrared field. This
contribution can be estimated using an universal formula and is found to
account for a substantial fraction of the measured delay.Comment: 4 pages, 4 figures, under consideratio
Diffuse large B-cell lymphoma of Waldeyer's ring has distinct clinicopathologic features: a GELA study
Background Diffuse large B-cell lymphomas (DLBCLs) arising in specific extranodal sites have peculiar clinicopathologic features. Patients and methods We analyzed a cohort of 187 primary Waldeyer's ring (WR) DLBCLs retrieved from GELA protocols using anthracyclin-based polychemotherapy. Results Most patients (92%) had stage I-II disease. A germinal center B-cell-like (GCB) immunophenotype was observed in 61%, and BCL2 expression in 55%, of WR DLBCLs. BCL2, BCL6, IRF4 and MYC breakpoints were observed in, respectively, 3 of 42 (7%), 9 of 36 (25%), 2 of 26 (8%) and 4 of 40 (10%) contributive cases. A variable follicular pattern was evidenced in 30 of 68 (44%) large biopsy specimens. The 5-year progression-free survival (PFS) and the overall survival (OS) of 153 WR DLBCL patients with survival information were 69.5% and 77.8%, respectively. The GCB immunophenotype correlated with a better OS (P=0.0015), while BCL2 expression predicted a worse OS (P=0.037), an effect overcome by the GCB/non-GCB classification. Compared with matched nodal DLBCLs, WR DLBCLs with no age-adjusted international prognostic index factor disclosed a better 5-year PFS rate (77.5% versus 70.7%; P=0.03). Conclusions WR DLBCLs display distinct clinicopathologic features compared with conventional DLBCLs, with usual localized-stage disease, common follicular features and a high frequency of GCB immunophenotype contrasting with a low rate of BCL2 rearrangements. In addition, they seem to be associated with a better outcome than their nodal counterpar
Photoemission time-delay measurements and calculations close to the 3s ionization minimum in Ar
We present experimental measurements and theoretical calculations of
photoionization time delays from the and shells in Ar in the photon
energy range of 32-42 eV. The experimental measurements are performed by
interferometry using attosecond pulse trains and the infrared laser used for
their generation. The theoretical approach includes intershell correlation
effects between the 3s and 3p shells within the framework of the random phase
approximation with exchange (RPAE). The connection between single-photon
ionization and the two-color two-photon ionization process used in the
measurement is established using the recently developed asymptotic
approximation for the complex transition amplitudes of laser-assisted
photoionization. We compare and discuss the theoretical and experimental
results especially in the region where strong intershell correlations in the 3s
to kp channel lead to an induced "Cooper" minimum in the 3s ionization
cross-section.Comment: submitted to PR
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
Role of the Renner-Teller effect after core hole excitation in the dissociation dynamics of carbon dioxide dication
The fragmentation of the doubly-charged carbon dioxide molecule is studied
after photoexcitation to the C 1s 12Ď€ u and O 1s 12Ď€ u states using a
multicoincidence ion-imaging technique. The bent component of the Renner-
Teller split states populated in the 1s→ π* resonant excitation at both the
carbon and oxygen 1sionization edges opens pathways to potential surfaces in
highly bent geometries in the dication. Evidence for a complete deformation of
the molecule is found in the coincident detection of C+ and O+2 ions. The
distinct alignment of this fragmentation channel indicates rapid deformation
and subsequent fragmentation. Investigation of the complete atomization
dynamics in the dication leading to asymmetric charge separation shows that
the primary dissociation mechanisms, sequential, concerted, and asynchronous
concerted, are correlated to specific fragment kinetic energies. The study
shows that the bond angle in fragmentation can extend below 20°
Rituximab retherapy in patients with relapsed aggressive B cell and mantle cell lymphoma
Neither effective salvage regimens nor the outcome and response to retherapy with rituximab containing chemotherapy have been defined for rituximab pre-treated patients with relapsing aggressive lymphoma. We report here a single-centre retrospective outcome analysis of second-line immunochemotherapy with rituximab. In 28 patients with relapsed or refractory diffuse large B cell lymphomas, first-line immunochemotherapy had induced objective responses in 18 patients. Nine of 28 patients responded to rituximab containing salvage therapy, leading to a median overall survival of 243Â days after start of second immunochemotherapy. Long-term disease free survivors (1,260 and 949Â days) were restricted to the group of twelve patients that had received allogeneic stem cell transplantation as consolidation therapy. In 21 patients with relapsed mantle cell lymphomas (MCL), 19 patients had reached remissions with first-line therapy. Of those, 16 patients experienced responses to salvage therapy with a median overall survival of 226Â days. Noteworthy, none of patients with initial non-responding disease reached a remission with second immunochemotherapy. Seven patients with MCL stayed free from progression after high-dose therapy with autologous or allogeneic stem cell transplantation in two and five cases, respectively. In summary, responses to repeated immunotherapy with rituximab were observed in approximately one third and two thirds of initially responding patients with aggressive B cell lymphoma and mantle cell lymphoma, respectively, but not in primarily refractory disease. Lasting remissions were achieved only by high-dose chemotherapy with stem cell transplantation
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