Asymmetry in the electron

To study the dipole moment of an electron, Nikhef researchers in this programme use polar molecules, such as barium fluoride (BaF). These molecules consist of atoms that are linked together by electromagnetic interaction and share one or more electrons. The molecule as a whole is electrically neutral, but the shared electrons within the molecule are subjected to a very strong electric field.

This strong internal electric field is used to measure whether the electron has an electric dipole moment. This is done using ultra-stable laser light, which allows the molecules to be placed in multiple quantum states simultaneously.

To prevent the molecules from moving too much during the measurement, the scientists are developing special cooling techniques to slow down and hold the molecules in place. These techniques are also used elsewhere to develop ultra-stable atomic clocks. In addition, this research programme is investigating whether new molecular systems can be found that enable even more sensitive measurements.

The increasingly sensitive measurements of the electron’s electric dipole moment within this Nikhef programme – in a global collaboration with complementary data from other teams – provide important new insights into the fundamental symmetries of particle physics. This approach, involving precision measurements of the quantum structure of molecules, is entirely complementary to traditional accelerator-based experiments.

The main location of the eEDM research programme is the Van Swinderen Institute for Particle Physics and Gravity at Nikhef partner the University of Groningen. A distinctive feature of the eEDM research programme is that theoretical and experimental experts within the project collaborate closely from various locations.

In the laboratory in Groningen, work is carried out using the central measurement setup for decelerating and trapping the molecules, and new laser techniques and measurement methods are being tested.

In the laser lab at VU University Amsterdam, molecular sources are being further developed, and work on the theoretical particle physics aspect of the programme is being carried out at the University of Amsterdam. The theoretical molecular chemistry required for the programme is being conducted at the Van Swinderen Institute (VSI) in Groningen, whilst Nikhef’s workshops in Amsterdam are closely involved in the technical upgrades of the experiment.

Researchers from the University of Groningen and Vrije Universiteit Amsterdam are participating in Nikhef’s eEDM research program.

Visit the eEDM experiment website: https://www.eedm.nl/