Cross sections for short pulse single and double ionization of helium

In a previous publication, procedures were proposed for unambiguously extracting amplitudes for single and double ionization from a time-dependent wavepacket by effectively propagating for an infinite time following a radiation pulse. Here we demonstrate the accuracy and utility of those methods for describing two-photon single and one-photon double ionization of helium. In particular it is shown how narrow features corresponding to autoionizing states are easily resolved with these methods.Comment: 9 pages, 9 figure

Photoabsorption cross sections of two-electron atoms by the coordinate rotation method: Application to H– and several states of He

The coordinate rotation method, recently extended by us to treat photoabsorption processes, is used to obtain photoabsorption cross sections for several two-electron atoms. The calculations are performed using standard configuration–interaction methods; the need for atomic continuum wavefunctions is completely avoided in this approach. We have computed the photodetachment cross section of H– and photoionization cross sections for He in its ground and 2 1S states. In all cases, the computed cross sections agree well with results obtained by numerical integration and with available experimental data

Decoding sequential vs non-sequential two-photon double ionization of helium using nuclear recoil

Above 54.4 eV, two-photon double ionization of helium is dominated by a sequential absorption process, producing characteristic behavior in the single and triple differential cross sections. We show that the signature of this process is visible in the nuclear recoil cross section, integrated over all energy sharings of the ejected electrons, even below the threshold for the sequential process. Since nuclear recoil momentum imaging does not require coincident photoelectron measurement, the predicted images present a viable target for future experiments with new short-pulse VUV and soft X-ray sources.Comment: 4 pages, 3 figure

A relationship between the many-body theory of inelastic scattering and the distorted wave approximation

It is shown that the first-order results of the recent many-body theory of inelastic scattering (see abstr. A25430 of 1971) can be derived by a direct application of the distorted-wave and random phase approximations to the usual expression for the inelastic scattering amplitude. The result is derived both in the second quantized formalism and by the standard application of the distorted-wave approximation coupled with the random phase approximation (RPA). The RPA (or time-dependent Hartree-Fock theory) provides the transition density between the initial and inelastically excited states. Possible generalizations of the procedures are discussed

A simple method for evaluating low-energy electron-molecule scattering cross sections using discrete basis functions

We present a simple, approximate method for calculating low-energy electron-molecule scattering cross sections using only the results of a basis set diagonalization of the molecular Hamiltonian. The method is based on the approximate conservation of orbital angular momentum in collisions between slow electrons and molecules lacking a permanent dipole moment (low l spoiling). Results are presented for e--H2, and e--N2, in the static-exchange approximation

The Lunar Orbital Prospector

The establishment of lunar bases will not end the need for remote sensing of the lunar surface by orbiting platforms. Human and robotic surface exploration will necessarily be limited to some proximate distance from the support base. Near real-time, high-resolution, global characterization of the lunar surface by orbiting sensing systems will continue to be essential to the understanding of the Moon's geophysical structure and the location of exploitable minerals and deposits of raw materials. The Lunar Orbital Prospector (LOP) is an orbiting sensing platform capable of supporting a variety of modular sensing packages. Serviced by a lunar-based shuttle, the LOP will permit the exchange of instrument packages to meet evolving mission needs. The ability to recover, modify, and rotate sensing packages allows their reuse in varying combinations. Combining this flexibility with robust orbit modification capabilities and near real-time telemetry links provides considerable system responsiveness. Maintenance and modification of the LOP orbit are accomplished through use of an onboard propulsion system that burns lunar-supplied oxygen and aluminum. The relatively low performance of such a system is more than compensated for by the elimination of the need for Earth-supplied propellants. The LOP concept envisions a continuous expansion of capability through the incorporation of new instrument technologies and the addition of platforms

Cross sections for the elastic scattering of low-energy electrons by molecular fluorine: an approximate theoretical treatment using discrete basis functions

Phaseshifts and total cross sections for the elastic scattering of low-energy (0-13.6 eV) electrons by molecular fluorine are presented. The phaseshifts are obtained by an approximate technique based on the weak asymptotic coupling of orbital angular momenta and are calculated solely from the results of a discrete basis set diagonalization of the molecular Hamiltonian. Correlation and polarization effects are not treated. The elastic cross section is dominated by a Sigma u+ shape resonance at about 2.2 eV in the static-exchange model

Successful Treatment of Primary Vaginal Papillary Serous Adenocarcinoma Using Chemoradiation Followed by Brachytherapy

Advances in treatment have not recently been reported in rare primary vaginal adenocarcinomas. A 56-year-old woman with a chronic vaginal cyst and possible in utero diethylstilbestrol exposure presented with postmenopausal bleeding. Biopsy of the vagina revealed high-grade papillary serous adenocarcinoma. MRI showed a 6-cm vaginal tumor and 3-cm left inguinal lymph node with metastasis. The patient initially received concurrent cisplatin and radiation. She then received high-dose-rate brachytherapy for further local control. Brachytherapy following external beam radiation with concurrent cisplatin led to clinically undetectable cancer at 24 months with minimal side effects