Multiphoton ionization of H2+ in the perturbative regime

2010 ◽  
Vol 88 (1) ◽  
pp. 1-7 ◽  
Author(s):  
Samira Barmaki ◽  
Stéphane Laulan
Keyword(s):  
Perturbation Theory ◽  
Cross Sections ◽  
Multiphoton Ionization ◽  
High Energy ◽  
High Energy Resolution ◽  
Resonance Structures ◽  
Internuclear Axis ◽  
Perturbative Regime ◽  
Photon Ionization ◽  
Ionization Processes

Multiphoton ionization of the H 2+ hydrogen molecular ion at fixed internuclear distance is investigated in the lowest order perturbation theory (LOPT). The parallel and perpendicular orientations between the polarization laser vector of the electric field and the H 2+ internuclear axis direction are considered. We calculate the generalized cross sections for the N = 2 to N = 6 photon ionization processes and we identify in each case the intermediate-state resonances. We show the efficiency of our method to describe resonance structures with high-energy resolution.

scholarly journals In-situ observation of trapped carriers in organic metal halide perovskite films with ultra-fast temporal and ultra-high energetic resolutions

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Kanishka Kobbekaduwa ◽  
Shreetu Shrestha ◽  
Pan Adhikari ◽  
Exian Liu ◽  
Lawrence Coleman ◽  
...  
Keyword(s):  
Cross Sections ◽  
High Energy ◽  
High Energy Resolution ◽  
In Situ Observation ◽  
Trap States ◽  
Tunneling Mechanism ◽  
Photocurrent Spectroscopy ◽  
Metal Halide Perovskite ◽  
Halide Perovskite

AbstractWe in-situ observe the ultrafast dynamics of trapped carriers in organic methyl ammonium lead halide perovskite thin films by ultrafast photocurrent spectroscopy with a sub-25 picosecond time resolution. Upon ultrafast laser excitation, trapped carriers follow a phonon assisted tunneling mechanism and a hopping transport mechanism along ultra-shallow to shallow trap states ranging from 1.72–11.51 millielectronvolts and is demonstrated by time-dependent and independent activation energies. Using temperature as an energetic ruler, we map trap states with ultra-high energy resolution down to < 0.01 millielectronvolt. In addition to carrier mobility of ~4 cm2V−1s−1 and lifetime of ~1 nanosecond, we validate the above transport mechanisms by highlighting trap state dynamics, including trapping rates, de-trapping rates and trap properties, such as trap density, trap levels, and capture-cross sections. In this work we establish a foundation for trap dynamics in high defect-tolerant perovskites with ultra-fast temporal and ultra-high energetic resolution.

scholarly journals FERMIONS IN THE INSTANTON-ANTI-INSTANTON VALLEY AND HIGH-ENERGY ELECTROWEAK INTERACTIONS

1994 ◽  
Vol 09 (15) ◽  
pp. 2613-2644
Author(s):  
RICCARDO GUIDA ◽  
KENICHI KONISHI
Keyword(s):  
Perturbation Theory ◽  
Correlation Function ◽  
Dirac Operator ◽  
Cross Sections ◽  
Theoretical Basis ◽  
High Energy ◽  
Electroweak Theory ◽  
Electroweak Interactions ◽  
Fermion Number ◽  
Chern Simons

We consider the behavior of fermions in the background of instanton-anti-instanton valley fields. Several different physics problems, from the high-energy electroweak interactions to the study of vacuum structure of QCD and of large orders of perturbation theory, are related to this problem. The spectrum of the Dirac operator in such a background is studied in detail. We present an approximation for the fermion correlation function when the instanton-anti-instanton separation (R) is large compared to their sizes (ρ). The situation where the instanton-anti-instanton overlap and melt is studied through the behavior of the Chern-Simons number as a function of R/ρ and x4. Applying our results to widely discussed cases of fermion-number violation in the electroweak theory, we conclude that there is no theoretical basis for expecting anomalous cross-sections to become observable at energies in the 10 TeV region.

scholarly journals A review of the fission programme at the CERN n_TOF facility

2019 ◽  
Vol 23 ◽  
pp. 16
Author(s):  
A. Tsinganis ◽  
For the N_TOF Collaboration
Keyword(s):  
Cross Sections ◽  
High Performance ◽  
Nuclear Astrophysics ◽  
Theoretical Models ◽  
High Energy ◽  
High Energy Resolution ◽  
Scientific Programme ◽  
Fuel Cycles ◽  
Accelerator Driven Systems ◽  
Radiative Neutron Capture

Since 2001, the scientific programme of the CERN n_TOF facility has focused mainly on the study of radiative neutron capture reactions, which are of great interest to nuclear astrophysics and on neutron-induced fission reactions, which are of relevance for nuclear technology, as well as essential for the development of theoretical models of fission. Taking advantage of the high instantaneous neutron flux and high energy resolution of the facility, as well as of high-performance detection and acquisition systems, accurate new measurements on several long-lived actinides, from 232Th to 245Cm, have been performed so far. Data on these isotopes are needed in order to improve the safety and efficiency of conventional reactors, as well as to develop new systems for nuclear energy production and treatment of nuclear waste, such as Generation IV reactors, Accelerator Driven Systems and reactors based on innovative fuel cycles. A review of the most important results on fission cross-sections and fragment properties obtained at n_TOF for a variety of isotopes is presented along with the perspectives arising from the newly added 19 m flight-path, which will expand the measurement capabilities to even more rare or short-lived isotopes, such as 230Th, 232U, 238Pu and 244Cm.

scholarly journals Multiphoton Ionization of Formaldehyde: Observation of 3py and 3pz Rydberg States

1987 ◽  
Vol 7 (1) ◽  
pp. 35-40 ◽  
Author(s):  
D. S. Bomse ◽  
S. Dougal
Keyword(s):  
Cross Sections ◽  
Vibrational Excitation ◽  
Multiphoton Ionization ◽  
Rydberg States ◽  
Resonant Absorption ◽  
Photon Excitation ◽  
Hot Band ◽  
Low Probability ◽  
Photon Ionization ◽  
Absorption Measurements

Multiphoton ionization (MPI) of CH2O and CD2O is reported for dye laser wavelengths between 445 and 470 nm. The ionization pathway starts with three-photon resonant absorption to 3py and 3pz Rydberg states. One or two additional photons are required, depending on wavelength, to reach threshold. MPI spectra agree well with VUV absorption measurements of the same Rydberg levels. MPI yields are small and photoacoustic measurements imply the initial three-photon excitation has low probability. Transitions at the four-photon ionization threshold show larger cross sections than the (overall) five-photon ionization bands but hot band transitions were not observed following selective vibrational excitation of ground state molecules.

Electron Probe and Auger Electron Microprobe Characterization of Modified Cu-Based Amorphous Alloys

2003 ◽  
Vol 9 (4) ◽  
pp. 359-367 ◽  
Author(s):  
A. Szummer ◽  
M. Janik-Czachor ◽  
P. Mack ◽  
M. Pisarek
Keyword(s):  
Surface Area ◽  
Cross Sections ◽  
Amorphous Alloys ◽  
Surface Oxidation ◽  
Auger Spectroscopy ◽  
High Energy ◽  
Careful Examination ◽  
High Energy Resolution ◽  
Air Exposure ◽  
Aging In Air

Changes in morphology and local chemical composition due to various methods of modification of surfaces of Cu-Zr, Cu-Hf, and Cu-Ti amorphous alloys (caused by aging in air/dry corrosion or hydrogen charging) were investigated. These modification/activation procedures transform the original amorphous ribbons of low surface area into efficient and stable catalysts, due to the segregation of a distinct amount of Cu and the development of a large specific surface area of Cu on a ZrOx or HfOx support. It was found that aging in air resulted in the formation of a bilayer of rough copper (containing small Cu particles indispensable for catalysis) on top of a rather smooth oxide underlayer (ZrOx, HfOx). Careful examination of the cross sections of the modified Cu-based ribbons revealed that, even after prolonged aging in air, only the first few microns of the surface layer was modified. Cu-Ti alloy was stable in air and did not undergo the expected modification. Hydrogenation followed by air exposure resulted in a disintegration of the ribbons into small pieces. Each piece was covered with many small Cu clusters 0.1–0.5 μm in diameter formed on an oxide underlayer. High-energy resolution Auger spectroscopy allowed identification of the underlayers (ZrO2, HfO2, or TiOx), identification of small Cu clusters, determination of the degree of surface oxidation of them, and mapping of the surface to identify the Cu-covered and “naked” heavy metal.

scholarly journals Resonance Neutron Capture in 86,87Sr

1982 ◽  
Vol 35 (3) ◽  
pp. 267 ◽  
Author(s):  
GC Hicks ◽  
BJ Allen ◽  
AR de L Musgrove ◽  
RL Macklin
Keyword(s):  
Cross Sections ◽  
Neutron Capture ◽  
High Energy ◽  
P Wave ◽  
High Energy Resolution ◽  
Electron Linear Accelerator ◽  
Resonance Neutron ◽  
Oak Ridge ◽  
Average Resonance ◽  
Capture Cross Sections

The neutron capture cross sections of 86.87Sr have been measured with high energy resolution from 3 to 200 keY at the 40 m station of the Oak Ridge Electron Linear Accelerator. Individual resonances were analysed to 37 keY for 86Sr and to 14 keY for 87Sr, and average resonance parameters were deduced on the basis of assumed divisions between s- and p-wave resonances. The average radiative widths obtained on this basis are consistent with a capture mechanism which is predominantly statistical

scholarly journals Resonance Neutron Capture in 138Ba and 140Ce and the Prompt Neutron Correction to ?-ray Detectors

1979 ◽  
Vol 32 (3) ◽  
pp. 213 ◽  
Author(s):  
AR de L Musgrove ◽  
BJ Alien ◽  
RL Macklin
Keyword(s):  
Cross Sections ◽  
Neutron Capture ◽  
High Energy ◽  
P Wave ◽  
Prompt Neutron ◽  
High Energy Resolution ◽  
Capture Cross ◽  
S Wave ◽  
Strength Functions ◽  
Capture Cross Sections

The neutron capture cross sections of 138Ba and 140Ce have been measured with high energy resolution between 3 and 100 keY using the capture cross section facility at the 40 m station of the Oak Ridge Electron Linear Accelerator. The average s-wave level spacings are <D)s = 6�3 � 1 �7 and 3�2 � 0�8 keY for 138Ba and 140Ce respectively. The deduced s-wave neutron strength functions are 104So = 1�0�0�4 and 1�54�0�53 respectively, and the average s-wave radiative widths are <r,)s = 55�20 and 35�9meY. The p-wave neutron strength functions are 104S1 ~ 0�03 and 0�32�0�12 respectively. The average 30 keY Maxwellian capture cross sections are 3�9�0�8mb for 138Ba and 7�7 � 0�9 mb for 140Ce. A more rigorous treatment of the prompt neutron correction for l'-ray detectors is described, and it is shown that previously published results for 138Ba have underestimated this correction. The 140Ce data provide excellent corroboration for the calculated magnitude and time dependence of the prompt neutron correction.

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