Enhanced sensitivity to variation of $m_{e}/m_{p}$ in molecular spectra
We propose new experiments with high sensitivity to a possible spatial or temporal variation of the electron-to-proton mass ratio $μ\equiv m_e/m_p$. We consider a nearly-degenerate pair of molecular vibrational levels, where each state is associated with a different electronic potential. The change in the splitting between such levels, with respect to a change in $μ$, can be large both on an absolute scale and relative to the splitting. We demonstrate the existence of such pairs of levels in Cs$_2$. The narrow spectral lines achievable with ultracold Cs$_2$ in these long-lived levels make this system promising for future searches for small variations in $μ$.
physics.atom-ph↗