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Université de Fribourg

Characterization of the global network of optical magnetometers to search for exotic physics (GNOME)

Afach, S. ; Budker, D. ; Camp, G. De ; Dumont, V. ; Grujić, Zoran Dragan ; Guo, H. ; Jackson Kimball, D. F. ; Kornack, T. W. ; Lebedev, Victor ; Li, W. ; Masia-Roig, H. ; Nix, S. ; Padniuk, M. ; Palm, C. A. ; Pankow, C. ; Penaflor, A. ; Peng, X. ; Pustelny, Simon ; Scholtes, Theo ; Smiga, J. A. ; Stalnaker, J. E. ; Weis, Antoine ; Wickenbrock, A. ; Wurm, D.

In: Physics of the Dark Universe, 2018, vol. 22, p. 162–180

The Global Network of Optical Magnetometers to search for Exotic physics (GNOME) is a network of geographically separated, time-synchronized, optically pumped atomic magnetometers that is being used to search for correlated transient signals heralding exotic physics. The GNOME is sensitive to nuclear- and electron-spin couplings to exotic fields from astrophysical sources such as compact...

Université de Fribourg

Quantitative study of optical pumping in the presence of spin-exchange relaxation

Shi, Yongqi ; Scholtes, Theo ; Grujić, Zoran D. ; Lebedev, Victor ; Dolgovskiy, Vladimir ; Weis, Antoine

In: Physical Review A, 2018, vol. 97, no. 1, p. 013419

We have performed quantitative measurements of the variation of the on-resonance absorption coefficients κ0 of the four hyperfine components of the Cs D1 transition as a function of laser power P, for pumping with linearly and with circularly polarized light. Sublevel populations derived from rate equations assuming isotropic population relaxation (at a rate γ1) yield algebraic κ0(P)...

Université de Fribourg

Orientational dependence of optically detected magnetic resonance signals in laser-driven atomic magnetometers

Colombo, Simone ; Dolgovskiy, Vladimir ; Scholtes, Theo ; Grujić, Zoran D. ; Lebedev, Victor ; Weis, Antoine

In: Applied Physics B, 2017, vol. 123, no. 1, p. 35

We have investigated the dependence of lock-in-demodulated Mx-magnetometer signals on the orientation of the static magnetic field B0 of interest. Magnetic resonance spectra for 2400 discrete orientations of B0 covering a 4π solid angle have been recorded by a PC-controlled steering and data acquisition system. Off-line fits by previously derived lineshape functions allow us to extract the...

Université de Fribourg

A magnetic source imaging camera

Dolgovskiy, Vladimir ; Fescenko, Ilja ; Sekiguchi, N. ; Colombo, Simone ; Lebedev, Victor ; Zhang, J. ; Weis, Antoine

In: Applied Physics Letters, 2016, vol. 109, no. 2, p. 023505

We describe a magnetic source imaging camera (MSIC) allowing a direct dynamic visualization of the two-dimensional spatial distribution of the individual components Bx(x,y), By(x,y) and Bz(x,y) of a magnetic field. The field patterns allow—in principle— a reconstruction of the distribution of sources that produce the field B→ by inverse problem analysis. We compare experimentally...

Université de Fribourg

M(H) dependence and size distribution of SPIONs measured by atomic magnetometry

Colombo, Simone ; Lebedev, Victor ; Grujic, Zoran Dragan ; Dolgovskiy, Vladimir ; Weis, Antoine

In: International Journal on Magnetic Particle Imaging, 2016, vol. 2, no. 1, p. -

We demonstrate that the quasistatic recording of the magnetic excitation function M(H) of superparamagnetic iron oxide magnetic nanoparticle (SPION) suspensions by an atomic magnetometer allows a precision determination of the sample’s iron mass contentmFe and the particle size distribution.

Université de Fribourg

MPS and ACS with an atomic magnetometer

Colombo, Simone ; Lebedev, Victor ; Grujic, Zoran Dragan ; Dolgovskiy, Vladimir ; Weis, Antoine

In: International Journal on Magnetic Particle Imaging, 2016, vol. 2, no. 1, p. -

We show that a single atomic magnetometer in a magnetically unshielded environment can be used to perform magnetic particle spectroscopy (MPS) and AC susceptometry (ACS) on liquid-suspended magnetic nanoparticles. We demonstrate methods allowing a simultaneous recording of M(H) and dM/dH(H) dependences of samples containing down to 1 μg of iron. Our results pave the way towards an atomic...

Université de Fribourg

A quantitative study of particle size effects in the magnetorelaxometry of magnetic nanoparticles using atomic magnetometry

Dolgovskiy, Vladimir ; Lebedev, Victor ; Colombo, Simone ; Weis, Antoine ; Michen, Benjamin ; Ackermann-Hirschi, Liliane ; Petri-Fink, Alke

In: Journal of Magnetism and Magnetic Materials, 2015, vol. 379, p. 137–150

The discrimination of immobilised superparamagnetic iron oxide nanoparticles (SPIONs) against SPIONs in fluid environments via their magnetic relaxation behaviour is a powerful tool for bio-medical imaging. Here we demonstrate that a gradiometer of laser-pumped atomic magnetometers can be used to record accurate time series of the relaxing magnetic field produced by pre-polarised SPIONs. We have...

Université de Fribourg

Spectroscopy of Mn atoms isolated in solid ⁴He

Moroshkin, Peter ; Lebedev, Victor ; Weis, Antoine

In: The Journal of Chemical Physics, 2014, vol. 140, no. 21, p. 214314

We present an experimental study of the laser-induced luminescence spectra of Mn atoms in solid helium matrices. We observe transitions of the valence electron and of inner-shell electrons. We find that the Mn-He interaction perturbs the inner-shell transitions to a lesser extent than the valence-electron transitions. The observed lineshapes of the inner-shell transitions of Mn are similar to...

Université de Fribourg

Non-Scanning magnetic field imaging with laser-pumped atomic magnetometer

Lebedev, Victor ; Dolgovskiy, V. ; Michen, B. ; Fink, Alke ; Bison, Georg ; Weis, Antoine

In: Biomedical Engineering / Biomedizinische Technik, 2013, p. -

We present first results on the imaging of the two dimensional magnetic field distributions using a recently developed magnetic field imaging camera (MFIC). The instrument is based on laser-pumped atomic magnetometry with an alkali vapour in a buffer gas. The device provides millimetre spatial and sub-second time resolution, and allows mapping the magnetic field from circa 2 cm2...