Constraints on exotic spin-dependent interactions between electrons from helium fine-structure spectroscopy

Agreement between theoretical calculations of atomic structure and spectroscopic measurements is used to constrain possible contribution of exotic spin-dependent interactions between electrons to the energy differences between states in helium-4. In particular, constraints on dipole-dipole interactions associated with the exchange of pseudoscalar bosons (such as axions or axion-like particles) with masses ${10}^{-2}\lesssim m\lesssim {10}^4\mathrm{eV}$ are improved by a factor of $\sim 100$. The first atomic-scale constraints on several exotic velocity-dependent dipole-dipole interactions are established as well.

Figure 1

Constraints (at the 90% confidence level) on the dimensionless coupling constant $g_3^e{g}_3^e/\left(4\pi \hslash c\right)$ as a function of the boson mass. The dashed line and dark gray fill shows the constraint for electrons from Ref. [35]. The dotted line and light gray fill show the constraint derived from analysis of positronium, also discussed in [35]. The solid line and medium gray fill shows the constraint from a comparison between theory and experiment for the $2^3{P}_2-2^3{P}_1$ transition frequency in He.

Figure 2

Constraints (at the 90% confidence level) on the dimensionless coupling constant $g_4^e{g}_4^e/\left(4\pi \hslash c\right)$ as a function of the boson mass coming from a comparison between theory and experiment for the $2^3{P}_2-2^3{P}_1$ transition frequency in He.

Figure 3

Constraints (at the 90% confidence level) on the dimensionless coupling constant $g_8^e{g}_8^e/\left(4\pi \hslash c\right)$ as a function of the boson mass coming from a comparison between theory and experiment for the $2^3{P}_2-2^3{P}_1$ transition frequency in He.

Figure 4

Constraints (at the 90% confidence level) on the dimensionless coupling constant $g_2^e{g}_2^e/\left(4\pi \hslash c\right)$ as a function of the boson mass. The dashed line and dark gray fill shows the constraint for electrons from Ref. [35]. The dotted line and light gray fill show the constraint derived from analysis of positronium, also discussed in [35]. The solid line and medium gray fill shows the constraint from a comparison between theory and experiment for the $2^3{S}_1-2^{3}P$ transition frequency in He.

Figure 5

Feynman diagram of an interaction between two electrons mediated by a light boson.