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PhD position (VU, Amsterdam): QED and the Proton Radius Puzzle

A four year, fully funded, PhD position in experimental physics is available. You will work in a team of four PhD and two postdocs, on potentially two …

bijna 4 jaar geleden


Van Vollenhovenlaan, Utrecht, Utrecht
Tijdelijk contract / Tijdelijke opdracht
Uren per week:
40 uur
€ 2937 - € 2937 per maand


A four year, fully funded, PhD position in experimental physics is available.

You will work in a team of four PhD and two postdocs, on potentially two projects. One is precision spectroscopy of molecular hydrogen in the deep-UV using advanced frequency comb laser methods to obtain a new value for the proton radius and perform new tests of molecular Quantum Electrodynamics. The other is precision spectroscopy in the extreme ultraviolet of a single trapped helium+ ion, based on amplified and unconverted pulses from an ultra-stable frequency comb laser. In this case we want to determine the alpha particle radius and perform the (ultimately) best test of bound state atomic Quantum Electrodynamics to search for new physics beyond the Standard Model.

The work is mainly experimental and involves many different aspects, such as developing cutting-edge ultrafast lasers and spectroscopy methods, nonlinear optics, electronics, atomic and molecular beam and trapping techniques, and much more.


The project is part of a NWO-I Programme that aims to solve the so called 'Proton Radius Puzzle' by highly-advanced precision spectroscopy in four different atoms and molecules: H2, HD+, He+ and He. This research takes place at LaserLaB Vrije Universiteit, in the Atomic, Molecular and Laser Physics group, and is a coordinated effort of all the PI's in the group and several external collaborators (at the ETH Zurich, PTB Braunschweig, University of Warsaw).

The proton radius puzzle emerged in 2010 when precision spectroscopy in normal (electronic) hydrogen and muonic hydrogen (where the electron is replaced with a muon) was used to test Quantum Electrodynamics (QED). The issue is that the finite size of the proton also causes small energy shifts in the spectrum, from which the proton size can actually be determined better than traditional electron scattering. However, the proton size obtained from electronic and muonic hydrogen spectroscopy differs by 4% (> 5 standard deviations), which is still a mystery.

With our research programme we want to obtain new values for the nuclear sizes of the proton, deuteron, alpha and helion particle at the attometer (10^-18 m) level. A comparison with results from muonic systems could unravel the puzzle, and also enable new tests of QED. For this challenge we have state of the art infrastructure, such as frequency comb lasers, an ultrastable laser (linewidth < 1 Hz, the only one in the Netherlands), a Cs atomic clock, and e.g. different forms of particle traps (ion traps, neutral atom/molecule traps) and (laser) cooling methods.


We seek excellent candidates which have a MSc in Physics (or similar, relevant for this position). Good verbal and written communication skills (in English) are required. Experience with (ultrafast) lasers and/or spectroscopy is an advantage, but most important is that you are, just like us, highly motivated and excited about the project.


When fulfilling a PhD position at NWO-I, the Institutes Organisation of NWO, you will get the status of junior scientist. You will have an employee status and can participate in all the employee benefits NWO-I offers. You will get a contract for four years.

Your salary will be up to a maximum of 2,937 euro gross per month. The salary is supplemented with a holiday allowance of 8 percent and an end-of-year bonus of 8.33 percent.

You are supposed to have a thesis finished at the end of your four year term with NWO-I. A training programme is part of the agreement. You and your supervisor will make up a plan for the additional education and supervising that you specifically need. This plan also defines which teaching activities you will be responsible (up to a maximum of ten percent of your time).

The conditions of employment of NWO-I are laid down in the Collective Labour Agreement for Research Centres (Cao-Onderzoekinstellingen), more exclusive information is available at this website under Personeelsinformatie (in Dutch) or under Personnel (in English). General information about working at NWO-I can be found in the English part of this website under Personnel. The 'Recruitment code' applies to this position.

Additional information

Prof.dr. Kjeld Eikema, group leader Ultrafast Laser Physics and Precision Metrology for Fundamental Tests. The preferred way of contact (initially) is by email.
For more informaton see our website.