An official website of the United States government
Ratios for target Ar K‐shell ionization associated with single and double electron capture, as well as the ratios corresponding to total capture and the projectile K x rays, were determined for 1.8‐ to 2.2‐MeV/u F7 + ,8 + ,9+projectiles. This work was performed at Western Michigan University with the tandem Van de Graaff accelerator. Coincidences between emitted K‐shell X‐rays (both target and projectile) and the corresponding charge‐changed particles were observed. The F9+Ar K X‐ray coincidence ratios for double to single capture are found to well exceed unity over the limited energy range of the measurements. Possible explanations for this anomalous behavior are discussed.
more »
« less
Differential Study of Projectile Coherence Effects on Double Capture Processes in p + Ar Collisions
We have measured differential yields for double capture and double capture accompanied by ionization in 75 keV p + Ar collisions. Data were taken for two different transverse projectile coherence lengths. A small effect of the projectile coherence properties on the yields were found for double capture, but not for double capture plus ionization. The results suggest that multiple projectile–target interactions can lead to a significant weakening of projectile coherence effects.
more »
« less
- Award ID(s):
- 1703109
- PAR ID:
- 10297359
- Date Published:
- Journal Name:
- Atoms
- Volume:
- 8
- Issue:
- 2
- ISSN:
- 2218-2004
- Page Range / eLocation ID:
- 10
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
-
Over the last decade, it has become clear that for heavy ion projectiles, the projectile’s transverse coherence length must be considered in theoretical models. While traditional scattering theory often assumes that the projectile has an infinite coherence length, many studies have demonstrated that the effect of projectile coherence cannot be ignored, even when the projectile-target interaction is within the perturbative regime. This has led to a surge in studies that examine the effects of the projectile’s coherence length. Heavy-ion collisions are particularly well-suited to this because the projectile’s momentum can be large, leading to a small deBroglie wavelength. In contrast, electron projectiles that have larger deBroglie wavelengths and coherence effects can usually be safely ignored. However, the recent demonstration of sculpted electron wave packets opens the door to studying projectile coherence effects in electron-impact collisions. We report here theoretical triple differential cross-sections (TDCSs) for the electron-impact ionization of helium using Bessel and Laguerre-Gauss projectiles. We show that the projectile’s transverse coherence length affects the shape and magnitude of the TDCSs and that the atomic target’s position within the projectile beam plays a significant role in the probability of ionization. We also demonstrate that projectiles with large coherence lengths result in cross-sections that more closely resemble their fully coherent counterparts.more » « less
-
Radiative double electron capture (RDEC), occurring when two electrons are captured to a projectile ion with the simultaneous emission of a single photon, has been investigated. RDEC can be considered as the time inverse process of double photoionization. Strong evidence for RDEC is found in F9++ N2collisions and additionally for one‐electron F8+for which the probability for the process is expected to be considerably smaller. Preliminary values for the cross sections for RDEC have been determined. A significant advantage of the gas target is that multiple‐collision effects seen for a solid target are avoided due to the single‐collision conditions that prevail for gas targets.more » « less
-
The ionization of CO, CO+, and CO2+ are quantified in an ultrafast, strong laser field. Measurements were performed over the intensity range from 1014 to 1017 W cm−2. Across this span, the intensity-dependent ionization yields were quantified over eight orders of magnitude in the dynamic range. Both sequential and (e, 2e) nonsequential ionization processes were observed. We calculate the electron states for CO and its molecular ions interacting with a strong laser field using a traditional field-free approach, the single active electron approximation, and present the results for the all-electron interaction of CO with the laser field. By comparing the calculated ionization with the experimental yields, we determined that the electron wave function polarization and Stark shifts were accurately treated with an all-electron Hartree–Fock calculation. The calculated field–molecule interaction included the core electron polarizability, which is not captured using field-free or frozen-core single-electron approximation.more » « less
-
We present momentum resolved covariance measurements of entangled electronic-nuclear wave packets created and probed with octave spanning phaselocked ultrafast pulses. We launch vibrational wave packets on multiple electronic states via multiphoton absorption, and probe these wave packets via strong field double ionization using a second phaselocked pulse. Momentum resolved covariance mapping of the fragment ions highlights the nuclear motion, while measurements of the yield as a function of the relative phase between pump and probe pulses highlight the electronic coherence. The combined measurements allow us to directly visualize the entanglement between the electronic and nuclear degrees of freedom and follow the evolution of the complete wavefunction. Published by the American Physical Society2024more » « less
- Free Publicly Accessible Full Text
-
Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.3390/atoms8020010
