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Theme 1 colloquium: 'Searching for new physics: towards extreme ultraviolet spectroscopy of a single helium+ ion' (Lecture)

Tuesday 2 July 2019Add to my calendar
from 16:00
prof. Kjeld Eikema (VU)

Kjeld EikemaMethods for spectroscopy have become ever more advanced and precise, especially after the invention of the frequency comb laser in 1999. Among the many applications of frequency combs is precise optical frequency measurement, and we use this to test fundamental physics and determine fundamental constants with table-top experiments. A very interesting target in this respect is a measurement of the 1S-2S transition in a single He+ ion. The challenge is that it requires extreme ultraviolet (<100 nm) to drive the transition, and the accuracy we aim for of 1 kHz is orders of magnitude better than demonstrated so far in this wavelength range. We developed a method, called Ramsey-comb spectroscopy, that enables us to do such precision measurements at short wavelengths. It is based on amplification and high-harmonic upconversion of two frequency-comb laser pulses. In the talk I will discuss how it works and present a recent demonstration measurement in xenon where we achieved the highest accuracy so far with light from high-harmonic generation. I will also discuss how we plan to use this method, and techniques such as quantum-logic state detection, to measure the 1S-2S transition in He+

dr. Gilles de Wijs