Context. Protostellar accretion discs have cool, dense midplanes where externally originating ionisation sources such as X–rays or cosmic rays are unable to penetrate. This suggests that for a wide range of radii, MHD turbulence can only be sustained in the surface layers where the ionisation fraction is sufficiently high. A dead zone is expected to exist near the midplane, such that active acc...

Context. The wings of Balmer lines are often used as effective temperature diagnostics for late-type (F, G, K) stars under the assumption they form in local thermodynamic equilibrium (LTE). Aims. Our goal is to investigate the non-LTE excitation and ionisation of hydrogen and the formation of Balmer lines in late-type stellar atmospheres, to establish if the assumption of LTE is justified. Furt...

Addition of a lipophilic ionic liquid to non-polar, hydrocarbon solvents (such as hexane and toluene) permits electrospray ionisation mass spectrometric analysis of dissolved analytes.

Single and multiple electron ionization of PF3 is characterized quantified by a joint computational experimental investigation. Absolute cross sections are presented the properties two low-lying dication states revealed.

Context. Recent observations of the X–ray emission from T Tauri stars in the Orion nebula have shown that they undergo frequent outbursts in their X–ray luminosity. These X–ray flares are characterised by increases in luminosity by two orders of magnitude, a typical duration of less than one day, and a significant hardening of the X–ray spectrum. Aims. It is unknown what effect these X–ray flar...

We use a combination of analytic and numerical arguments to consider the impact of quasar photo-heating during He II reionisation on the thermal evolution of the intergalactic medium (IGM). We demonstrate that rapid (∆z < 0.1–0.2), strong (∆T > 10 K) photo-heating is difficult to achieve across the entire IGM unless quasar spectra are significantly harder than implied by current observational c...