Related papers: New effective recombination coefficients for nebul…
We have measured resonance strengths and energies for dielectronic recombination (DR) of Mg-like Fe XV forming Al-like Fe XIV via N=3 -> N' = 3 core excitations in the electron-ion collision energy range 0-45 eV. All measurements were…
A method is presented to derive electron temperatures and densities of planetary nebulae (PNe) simultaneously, using the observed hydrogen recombination spectrum, which includes continuum and line emission. By matching theoretical spectra…
Photoionization and its inverse, electron-ion recombination, are key processes that influence many astrophysical plasmas (and gasses), and the diagnostics that we use to analyse the plasmas. In this review we provide a brief overview of the…
We present results of deep echelle spectrophotometry of eight Galactic HII regions located at Galactocentric distances between 6.3 and 10.4 kpc. The data have been taken with the Very Large Telescope (VLT) Ultraviolet Echelle Spectrograph…
At intermediate to high densities, electron (de-)excitation collisions are the dominant process for populating or depopulating high Rydberg states. In particular, the accurate knowledge of the energy changing ($n$-changing) collisional…
We report the first unambiguous observational evidence of Rydberg Enhanced Recombination (RER), a potentially important recombination mechanism that has hitherto been unexplored in low-temperature photoionized plasmas. RER shares…
The nebular spectra of Type Ia supernovae ($\gtrapprox$ 100 days after explosion) consist mainly of emission lines from singly- and doubly-ionised Fe-group nuclei. However, theoretical models for many scenarios predict that non-thermal…
We report measurements of resonant low-energy electron attachment to O\(_2\) molecular impurities in neon gas in the temperature range \(46.5\,\mbox{K}\le T\le 101\,\mbox{K}\). The reduced attachment frequency \(\nu_A/N\) shows a well…
Absolute cross sections for the K-shell photoionization of ground-state Li-like carbon [C$^{3+}$(1s$^2$2s $^2$S)] ions were measured by employing the ion-photon merged-beams technique at the Advanced Light Source. The energy ranges…
Accurate calculation of the ion-ion recombination rate coefficient has been of long-standing interest, as it controls the ion concentration in gas phase systems and in aerosols. We describe the development of a hybrid continuum-molecular…
We present a method for deriving the electron density of ionized gas using the ratio of the intensity of the [NII] 205um line to that of Hydrogen radio recombination lines (RRL). We use this method to derive electron densities of 21…
The current paper presents atomic data generated to investigate the recombination lines of C II in the spectra of planetary nebulae. These data include energies of bound and autoionizing states, oscillator strengths and radiative transition…
A significant fraction of the molecular gas in star-forming regions is irradiated by stellar UV photons. In these environments, the electron density (n_e) plays a critical role in the gas dynamics, chemistry, and collisional excitation of…
We have measured electron-ion recombination for Fe XII forming Fe XI using a merged beams configuration at the heavy-ion storage ring TSR located at the Max Planck Institute for Nuclear Physics in Heidelberg, Germany. The measured merged…
We present high quality optical spectroscopic observations of the planetary nebula (PN) Hf 2-2. The spectrum exhibits many prominent optical recombination lines (ORLs) from heavy element ions. Analysis of the H {\sc i} and He {\sc i}…
We have studied radiofrequency capacitively coupled plasmas in pure O2 using single mode laser cavity ringdown spectroscopy of oxygen atoms at 630 nm. The absolute atom densities and translational temperatures were determined over a range…
The basic approach for measuring electron-ion recombination rate coefficients in merged-beams electron-ion collision experiments at heavy-ion storage rings is outlined. As an example experimental results for the low temperature…
The electron density ($n_{e^{-}}$) plays an important role in setting the chemistry and physics of the interstellar medium. However, measurements of $n_{e^{-}}$ in neutral clouds have been directly obtained only toward a few lines of sight…
Spectroscopic studies of extreme-ionization galaxies (EIGs) are critical to our understanding of exotic systems throughout cosmic time. These EIGs exhibit spectral features requiring >54.42 eV photons: the energy needed to fully ionize…
We have investigated the effects of a non-thermal electron population on the ionization and recombination rates. The considered electron distribution is defined as a Maxwellian function below a break energy E_b and as a power-law function…