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We perform ab initio QED calculations of energy levels for the n = 1 and n = 2 states of He-like ions with the nuclear charge in the range Z = 12-100. The complete set of two-electron QED corrections is evaluated to all orders in the parameter αZ. Uncalculated contributions to energy levels come through orders α 3 (αZ) 2 , α 2 (αZ) 7 , and higher. The calculation presented is the first treatment for excited states of He-like ions complete through order α 2 (αZ) 4 . A significant improvement in accuracy of theoretical predictions is achieved, especially in the high-Z region.

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A new approach to finite basis sets for the Dirac equation is developed. It solves the problem of spurious states and, as a result, improves the convergence properties of basis set calculations. The efficiency of the method is demonstrated for finite basis sets constructed from B splines by calculating the one-loop self-energy correction for a hydrogenlike ion.

In particular the creation of photons in vibrating cavities seems to be the most promising scenario for a possible experimental verification of motion-induced vacuum radiation (see e.g. [7][8][9][10][11]). 1The thermodynamics of the static Casimir effect has been investigated intensively (see e.g. [13] and references therein). In that context temperature effects are known to even dominate the pure vacuum effect (at T = 0) and, in consequence, have to be taken into account when analysing the data in measurements of the static Casimir force. In contrast to this the dynamical Casimir effect at finite temperature so far has not been subject of research. It has been anticipated in a recent investigation by Lambrecht et al.[12] that temperature effects could play an important role for the generation of a photon pulse in a vibrating Fabry-Pérot cavity. However, realistic calculations of thermal effects on quantum radiation within the framework of quantum field theory of time-dependent systems at finite temperature are not yet available.Accordingly, it is our major intention to close this gap and to provide a generalization of the Hamiltonian approach presented recently in Refs. [14,15]. In this letter we focus the discussion predominantly on results obtained for the thermal contribution to photon production in a resonantly vibrating cavity as one of the most relevant configuration when aiming for experimental tests of the dynamical Casimir effect [9]. We like to address the question whether or not the effect of quantum radiation might be covered by the thermal background and we will examine the conditions under which it remains most significant even