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Light can hold an atom in place, just like a jet of air holds a lightweight ball. But a dysprosium atom is no ordinary ball: inside it has many "gears" (electrons) that respond differently to light of different colors. To catch such an atom and keep it from slipping away, you need to know exactly how strongly the light pulls on it.

Scientists used a laser with a wavelength of 530.306 nanometers: that's green light, slightly more blue than the color of fresh grass. They directed it at a dysprosium atom and measured how the atom's energy changes depending on the light's polarization (how the light wave "twists"). They got two numbers: one shows the overall attraction, the other shows the difference for different states of the atom. These numbers matched calculations based on the theory of atomic structure.

Why does this matter? Such measurements allow building optical tweezers — traps where each atom sits in its own "nest" of light. If you know the force of attraction in advance, you can arrange atoms neatly like pieces on a chessboard and make them interact with each other. This is a step toward quantum computing, where atoms act as qubits.

Now engineers have verified numbers for green light, and they can design traps for dysprosium more precisely than before.

Original abstract

as written by the authors arXiv:2604.03177

Open-shell lanthanide atoms, and dysprosium in particular, combine a large ground-state angular momentum with dense electronic spectra, making their dynamical polarizability strongly dependent on wavelength and internal state and therefore particularly challenging to characterize accurately. This issue has become especially relevant with the recent development of single-atom trapping of dysprosium in optical-tweezer arrays, where precise knowledge of the polarizability is needed to design optimized trapping architectures. Here, we exploit the strong spin-dependent light shift near the $$J'=J-1$$ intercombination line at 530.306 nm to determine the background scalar and vector polarizabilities of $$^{162}$$Dy in its ground state near this wavelength. Our measurements quantitatively agree with atomic-structure calculations and provide new insight into the contributions of nearby transitions in a spectral region relevant to emerging dysprosium tweezer platforms.