Andrew U. Hazi

Scaling the Yield of Laser-Driven Electron-Positron Jets to Laboratory Astrophysical Applications

We report new experimental results obtained on three different laser facilities that show directed laser-driven relativistic electron-positron jets with up to 30 times larger yields than previously obtained and a quadratic (∼E_{L}^{2}) dependence of the positron yield on the laser energy. This favorable scaling stems from a combination of higher energy electrons due to increased laser intensity and the recirculation of MeV electrons in the mm-thick target. Based on this scaling, first principles simulations predict the possibility of using such electron-positron jets, produced at upcoming high-energy laser facilities, to probe the physics of relativistic collisionless shocks in the laboratory.

Conversion of bound states to resonances with changing internuclear distance in molecular anions

The complex self‐consistent field (CSCF) method has been used to compute the complex potential‐energy curves of the lowest 2Σ+u autodetaching resonance state of F−2 and the 2Πg resonance state of N−2. The calculated width of the 2Πg resonance of N−2 as a function of internuclear distance is in excellent agreement with the results of previous calculations by other methods. The SCF energies of the anion and the neutral molecule in these examples cross at an internuclear distance different from that at which the SCF energy of the anion becomes complex. We find this to be a general feature of the SCF description of shape resonance states. Correlation effects appear to be of critical importance in determining the behavior of the resonance states in the crossing region.

2Σ+ and 2Π states of LiF−

Large and diffuse molecular orbital basis sets have been used to study the electronic states of LiF− arising from the Li+F− asymptotes. The 2Σ+ ground state is bound relative to LiF(X 1Σ+) by 0.33 eV, in agreement with previous calculations. The excited 2Σ+ and 2Π states, which arise from the Li(2P)+F−(1S) asymptote, also remain bound relative to the ground state of LiF as the internuclear distance decreases from 20 to 5a0; however, the corresponding 6σ and 2π orbitals change drastically from a 2p orbital localized on the Li atom to very diffuse ’’dipole’’ states. At R = 2.988a0, the 2 2Σ+ state of LiF− has a binding energy of at least 4.2 meV relative to the neutral molecule. We found no evidence of shape resonances in the electron‐scattering continuum of LiF(X 1Σ+), in contrast to previous results obtained with limited basis sets.

Velocity distribution of H(2s) resulting from the electron impact dissociation of H2

We have calculated the velocity distribution of the fast, metastable hydrogen and deuterium atoms which result from the dissociation of the 1Πu(2pπu, 2sσg) autoionizing states of H2 and D2. The present model uses the previously computed potential energy curve and autoionization width of this doubly excited 1Πu state. The model treats the competition between ionization and dissociation into neutral fragments classically. In calculating the laboratory velocity distribution we take into account the thermal motion of the target molecules and the recoil due to the scattered electron. The effect of momentum transfer is important, as the calculated laboratory speed distribution depends sensitively on the angle of detection. The comparison of the experimental and the theoretical velocity distributions shows a significant discrepancy among the three measurements which have been reported to date.

Photodetachment cross section of Cu

We report the first ab initio calculation of the photodetachment cross section of the bound

Oxygen K hole photoionization cross section of CO2

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No pain—no gain: The complex art of soft x‐ray laser target design and analysis

ion. The calculated cross section exhibits two shape resonances, the larger of which should be accessible experimentally. The magnitude of the cross section is substantial [(6.8-7.1) \ifmmode\times\else\texttimes\fi{}

The unexpected role of evolving longitudinal electric fields in generating energetic electrons in relativistically transparent plasmas

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Two-dimensional time-resolved ultra-high speed imaging of K-alpha emission from short-pulse-laser interactions to observe electron recirculation

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