A. Hirtl

Hadronic shift in pionic hydrogen

The hadronic shift in pionic hydrogen has been redetermined to be ε1s = 7.086 ± 0.007(stat) ± 0.006(sys) eV by X-ray spectroscopy of ground-state transitions applying various energy calibration schemes. The experiment was performed at the high-intensity low-energy pion beam of the Paul Scherrer Institut by using the cyclotron trap and an ultimate-resolution Bragg spectrometer with bent crystals.

He-like argon, chlorine and sulfur spectra measurement from an Electron Cyclotron Resonance Ion Trap

We present a new measurement on X-ray spectroscopy of multicharged argon, chlorine and sulfur obtained with the Electron Cyclotron Resonance Ion Trap installed at the Paul Scherrer Institut (Villigen, Switzerland). For this purpose, we used a crystal spectrometer with a spherically bent crystal having an energy resolution of about 0.4 eV. High intensity Kα X-ray spectra were obtained from ions with one 1s hole ranging from almost neutral to heliumlike charge states. In particular we observed the 1s2s 3 S1 → 1s 21 S0 M1 and 1s2p 3 P2 → 1s 21 S0 M2 transitions in He-like argon, chlorine and sulfur with unprecedented statistics and resolution. The preliminary analysis presented here describes a new technique to measure precisely energy differences between transitions using a Johann-type Bragg spectrometer. A recent characterization of the spectrometer will allow for a drastic reduction of the systematic errors.

Precision measurements in pionic hydrogen

Abstract The strong interaction in the pion nucleon system leads to a shift and a broadening of the 1s-ground state in pionic hydrogen. These two quantities are being measured in an experiment at the Paul Scherrer Institute with much improved precision and allow an experimental test of recent calculations in the framework of Chiral Perturbation Theory. The experimental techniques using high resolution crystal spectroscopy are described as well as recent results.

Highly charged ion X-rays from Electron–Cyclotron Resonance Ion Sources

Abstract Radiation from the highly charged ions contained in the plasma of Electron–Cyclotron Resonance Ion Sources (ECRISs) constitutes a very bright source of X-rays. Because the ions have a relatively low kinetic energy ( ≈ 1 eV ) transitions can be very narrow, containing only a small Doppler broadening. We describe preliminary accurate measurements of two and three-electron ions with Z = 16 – 18 . We show how these measurement can test sensitively many-body relativistic calculations or can be used as X-ray standards for precise measurements of X-ray transitions in exotic atoms.

High-precision x-ray spectroscopy in few-electron ions

The experimental and spectrum analysis procedures that led to about 15 new, high-precision, relative x-ray line energy measurements are presented. The measured lines may be used as x-ray reference lines in the 2.4?3.1?keV range. Applications also include tests of the atomic theory, and in particular of quantum electrodynamics and of relativistic many-body theory calculations. The lines originate from 2- to 4-electron ions of sulfur (Z=16), chlorine (Z=17) and argon (Z=18). The precision reached for their energy ranges from a few parts per million (ppm) to about 50?ppm. This places the new measurements among the most precise performed in mid-Z highly charged ions (Z is the nuclear charge number). The elements of the experimental setup are described: the ion source (an electron cyclotron resonance ion trap), the spectrometer (a single, spherically bent crystal spectrometer), as well as the spectrum acquisition camera (low-noise, high-efficiency CCD). The spectrum analysis procedure, which is based on a full simulation of the spectrometer response function, is also presented.

Conclusions from recent pionic--atom experiments

The most recent pionic—hydrogen experiment marks the completion of a whole series of measurements, the main goal of which was to provide conclusive data on pion—nucleon interaction at threshold for comparison with calculations from Chiral perturbation theory. The precision achieved for hadronic shift and broadening of 0.2% and 2%, respectively, became possible by comprehensive studies of cascade effects in hydrogen and other light exotic atoms including results from the last years of LEAR operation. In order to obtain optimum conditions for the Bragg crystal spectrometer, the cyclotron trap II has been used to provide a suitable X—ray source. To characterize the bent crystal spectrometer, the cyclotron trap has been modified to operate as an electron—cyclotron resonance source, which produces with high intensity narrow X‐ray transitions in the few keV range originating from highly charged ions.

High Resolution He‐like Argon And Sulfur Spectra From The PSI ECRIT

We present new results on the X‐ray spectroscopy of multicharged argon, sulfur and chlorine obtained with the Electron Cyclotron Resonance Ion Trap (ECRIT) in operation at the Paul Scherrer Institut (Villigen, Switzerland). We used a Johann‐type Bragg spectrometer with a spherically‐bent crystal, with an energy resolution of about 0.4 eV. The ECRIT itself is of a hybrid type, with a superconducting split coil magnet, special iron inserts which provides the mirror field, and a permanent magnetic hexapole. The high frequency was provided by a 6.4 GHz microwave emitter.We obtained high intensity X‐ray spectra of multicharged F‐like to He‐like argon, sulfur and chlorine with one 1s hole. In particular, we observed the 1s2s 3S1 → 1s2 1S0 M1 and 1s2p 3P2 → 1s2 1S0 M2 transitions in He‐like argon, sulfur and chlorine with unprecedented statistics and resolution. The energies of the observed lines are being determined with good accuracy using the He‐like M1 line as a reference.We surveyed the He‐like M1 transitio...

Precision measurement of the (3p–1s) X-ray transition in muonic hydrogen

The (3p — 1s) X-ray transition to the muonic hydrogen ground state was measured with a highresolution crystal spectrometer. The assumption of a statistical population of the hyperfine levels of the muonic hydrogen ground state was directly confirmed by the experiment and measured values for the hyperfine splitting can be reported. The measurement supplements studies on line broadening effects induced by Coulomb de-excitation hindering the direct extraction of the pion-nucleon scattering lengths from pionic hydrogen and deuterium X-ray lines.

Line shape analysis of the Kβ transition in muonic hydrogen

Abstract The Kβ transition in muonic hydrogen was measured with a high-resolution crystal spectrometer. The spectrum is shown to be sensitive to the ground-state hyperfine splitting, the corresponding triplet-to-singlet ratio, and the kinetic energy distribution in the 3p state. The hyperfine splitting and triplet-to-singlet ratio are found to be consistent with the values expected from theoretical and experimental investigations and, therefore, were fixed accordingly in order to reduce the uncertainties in the further reconstruction of the kinetic energy distribution. The presence of high-energetic components was established and quantified in both a phenomenological, i.e. cascade-model-free fit, and in a direct deconvolution of the Doppler broadening based on the Bayesian method. Graphical abstract

Chapter 11 Experiments on Highly Charged Heavy Ions in Conjunction with Exotic Atoms

We demonstrate how combining highly-charged ions and exotic atoms measurements can provide high-accuracy information on particle properties, like the pion mass, on interactions, like the pion-proton strong interaction at low energy, and bound-state QED in strong fields. The use of highly-charged ion X-rays emitted by the plasma inside a super-conducting ion source provides a very detailed characterization of the response function of the X-ray spectrometer used to study exotic atoms, allowing for very accurate measurements. Conversely the use of the same high-resolution and high transmission spectrometer provides very accurate measurements of X-ray lines of few-electron ions.