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Precision Laser Spectroscopy in the Extreme Ultraviolet

  1. Kjeld S.E. Eikema,
  2. Wim Ubachs

Published Online: 15 SEP 2011

DOI: 10.1002/9780470749593.hrs079

Handbook of High-resolution Spectroscopy

Handbook of High-resolution Spectroscopy

How to Cite

Eikema, K. S. and Ubachs, W. 2011. Precision Laser Spectroscopy in the Extreme Ultraviolet. Handbook of High-resolution Spectroscopy.

Author Information

  1. Vrije Universiteit, Department of Physics and Astronomy, Amsterdam, The Netherlands

Publication History

  1. Published Online: 15 SEP 2011

Abstract

Techniques for the production of short wavelengths in the extreme ultraviolet wavelength range are described, spanning low-order harmonic generation in the perturbative regime for narrow bandwidth XUV production to the plateau-regime with the three-step collisional model for the generation of high harmonics with broadband ultrafast pulses. In addition, the intermediate regime is discussed for pulses of 300 ps duration, as well as the regime of harmonic conversion based on continuous wave lasers aiming at the production of coherent Lyman-α radiation. Applications of XUV sources in the frequency domain typically rely on the production of XUV-light from narrowband Fourier-transform-limited pulses for recording high-resolution spectra. Alternatively, harmonically upconverted pulses of ultrashort duration (with inter-pulse coherence) can be used for spectroscopic studies in the time and frequency domain (such as direct frequency comb spectroscopy techniques). Examples of both approaches for atomic and molecular spectroscopy are discussed at some length. For precision metrology on atomic systems, a focus is put on the Lamb shift determination in the He ground state. In the realm of molecular spectroscopy, predissociation phenomena in the nitrogen molecule are highlighted, with relevance for dissociation processes occurring in the upper layers of the Earth atmosphere. Similar predissociation phenomena in carbon monoxide are also treated in some detail, in this case with relevance for the chemistry in interstellar clouds. Precision XUV spectroscopy of molecular hydrogen is discussed as well, as it relates to the possibility of detecting a variation of the proton–electron mass ratio on a cosmological time scale. In the last section, applications of direct frequency comb spectroscopic techniques at short wavelengths are explained and prospects are given for using these techniques at extreme ultraviolet wavelengths.

Keywords:

  • extreme ultraviolet;
  • vacuum ultraviolet;
  • laser spectroscopy;
  • harmonic generation;
  • predissociation;
  • line broadening;
  • frequency comb lasers;
  • direct frequency comb spectroscopy