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High-resolution Auger spectra of doubly excited Be-like neon have been obtained for intermediate collisional velocities (0.89--1.79 a.u.). Ne[sup 8+] was produced at high voltage in the Argonne National Laboratory electron-cyclotron-resonance ion source. A differentially pumped helium gas cell was used to study double electron capture. The [ital LMX] Auger decays of the Be-like neon are observed with a high-resolution 0[degree] tandem electron spectrometer. High-angular-momentum states are observed to be populated during the collisions and their relative amplitudes change dramatically with increasing collisional velocity.

The hyperfine structures of six metastable levels arising from the 3{ital d}{sup 2}4{ital s} and 3{ital d}{sup 3} configurations in {sup 49}Ti II have been measured with high precision using the laser-rf double-resonance technique in a collinear laser--ion-beam geometry. The hfs constants {ital A} and {ital B} were determined to about 4 and 43 kHz, respectively. Less precise results are also reported for the 2{ital p}{sub 1/2} level of the 3{ital d}{sup 3} configuration and for five upper levels in the 3{ital d}{sup 2}4{ital p} configuration. For these states, the optical spectra had Doppler widths of about 40 MHz, leading to {ital A} values determined to about 1 MHz. The results are compared with the presently available Hartree-Fock (HF) calculations. Good agreement is obtained with the HF results only in some cases. Substantial corrections due to many-body interactions and relativistic effects are required for other cases.

High-resolution 0{degree} Auger spectroscopy has been used to study the Ne {ital LMM} and {ital LMN} Auger emission. The doubly excited states in B-like Ne are produced via nonresonant transfer and excitation (NTE) in collisions of 15 to 60-keV/amu Ne{sup 6+} incident on He. Line assignments are given for Auger transitions observed in the energy range between 20 and 100 eV, and capture into a triplet state is observed. The relative cross sections for these rates show a broad ({gt}300 keV full width at half maximum) asymmetrical shape as a function of projectile energy, characteristic of the NTE process.

The Auger spectrum and the relevant angular distribution and spin polarization parameters have been obtained, both, experimentally and numerically for the resonant Auger decay of the photoexcited Ar*(2p3/2−14s1/2)J=1 state. The experiment has been performed using linearly and circularly polarized light and by means of a time‐of‐flight electron analyzer and a Mott polarimeter. The dynamical as well as the transferred spin polarization of the emitted electrons have been determined. The theoretical data have been obtained within a relativistic distorted wave approximation applying a relaxed orbital method. Our numerical results obtained within an 8 configuration state function calculation are compared to the experimental data for the transferred spin polarization. Good agreement to the experiment has been found. Though single fine structure lines show a large dynamic spin polarization the theoretical data yield almost vanishing dynamic spin polarization for the Auger lines. A detailed analysis in terms of pa...

We have applied the laser-rf-laser double-resonance method to a molecular ion. Fifty-six hyperfine components of fine-structure transitions (\ensuremath{\Delta}J=\ifmmode\pm\else\textpm\fi{}1) were measured in rotational levels from N=1 to 27 of the \ensuremath{\nu}''=1 vibrational level of the ${\mathit{X}}^{2}$ ${\mathrm{\ensuremath{\Sigma}}}_{\mathit{g}}^{+}$ ground electronic state of $^{14}\mathrm{N}_{2}^{+}$. In order to fit the data, we required seven molecular constants, corresponding to the following interactions: electron spin-rotation fine structure and its centrifugal distortion, Fermi-contact hyperfine structure (hfs), dipolar hfs and its centrifugal distortion, and electric quadrupole and nuclear spin-rotation hfs. The results are in reasonable agreement with theoretical calculations based upon a Hartree-Fock-Roothaan wave function.

Ne clusters (∼5000 atoms) were resonantly excited (2p→3s) by intense free electron laser (FEL) radiation at FERMI. Such multiply excited clusters can decay nonradiatively via energy exchange between at least two neighboring excited atoms. Benefiting from the precise tunability and narrow bandwidth of seeded FEL radiation, specific sites of the Ne clusters were probed. We found that the relaxation of cluster surface atoms proceeds via a sequence of interatomic or intermolecular Coulombic decay (ICD) processes while ICD of bulk atoms is additionally affected by the surrounding excited medium via inelastic electron scattering. For both cases, cluster excitations relax to atomic states prior to ICD, showing that this kind of ICD is rather slow (picosecond range). Controlling the average number of excitations per cluster via the FEL intensity allows a coarse tuning of the ICD rate.