Jobs: 1 Postdoc position: not available
This position has been filled and is no longer available.
Position: Postdoc on 1S-2S
spectroscopy of trapped He+ (and possibly H2
spectroscopy) for fundamental tests.
Funded by NWO and ERC.
This postdoc position is available at the experiment
where we want to excite the 1S-2S transition in a single
He+ ion. This ion will be trapped in an advanced Paul
trap (a collaboration with PTB, the groups of prof.
Mehlstaubler and prof Schmidt), and we will excite the
two-photon transition with a combination of 32 nm made
by High-Harmonic Generation (HHG) and 790 nm (the
high-power fundamental wavelength used for HHG). We
spectroscopy, which was developed in our group.
The whole experiment involves many techniques, such as a
frequency comb laser, high-power parametric laser pulse
amplification, an ultra-stable laser, laser cooling at
313 nm, side-band cooling, ultra-high vacuum,
quantum-optics, high-harmonic generation, and so much
more! We have quite unconventional ideas how to realize
the first excitation of He+ from the ground state. The
target accuracy is 1 kHz or better. We want to use the
measurement to check the predictions by theory, and look
for new physics. This is done by comparing the results
with other determinations, e.g. in atomic hydrogen,
muonic hydrogen, and muonic helium+. This will able us
to check the value of the Rydberg constant (it shifted
more than 5 sigma in the CODATA 2018 evaluation!), the
charge radius of the alpha particle, and test
Apart from the He+ experiment, there is also the
possibility to work on excitation of the EF-X transition
of para and ortho H2 (at 202 nm) to determine its
dissociation energy for a comparison with theory (a test
of quantum-molecular calculations and QED).
You can read more about the He+ experiment here, and
about the H2 experiment here.
Below: the High-Harmonic Generation and excitation setup
for He+ spectroscopy (in a configuration for a precursor
experiment with Xe).
the Postdoc position:
You should have a PhD in physics with
optics/spectroscopy experience and preferably with
Paul-trap experience. You should enjoy challenges and be
enthusiastic about this intriguing project. The project
is a real team effort, so you should feel comfortable
working with 2 PhD students and 1-2 postdocs on this
project. Even if you have no experience with Paul traps
for precision spectroscopy, you can still apply! Most
important is that you are bright, enthusiastic, work
well in a team, and are eager to learn.
More information about salary will be posted shortly,
but it is the usual salary for a Postdoc in the
Netherlands at a university.
Below: Former PhD student Laura
Dreissen working in the He+/Xe setup, installing a
time-of-flight mass spectrometer for the experiment
where we demonstrated a key ingredient of the upcoming
He+ experiment: Ramsey-comb spectroscopy with light
produced by High-Harmonic generation. The results
where published in Phys.
Rev. Lett. (2019), and Phys.
Rev. A. (2020).
conditions of employment
You can find information about
the side benefits at
The project and position is based in the LaserLaB Vrije
The Vrije Universiteit
Amsterdam is a leading, innovative and growing university
that is at the heart of society and actively contributes
to new developments in teaching and research. Our
university has ten faculties which span a wide range of
disciplines, as well as several institutes, foundations,
research centers, and support services. Its campus is
located in the fastest-growing economic region in the
Netherlands (the Zuidas district of Amsterdam), and
provides work for over 4,500 staff and scientific
education for more than 23,000 students.
deadline is 1 December 2020.
Evaluations take place
continuously, but as long as this message is
visible, the position is still open.
Send your application to prof. dr. Kjeld Eikema,
Please include a letter of motivation, CV, and 2 names
with email addresses of people as a reference.