SeD Radical: A probe for measurement of time variation of Fine Structure Constant($α$) and Proton to Electron Mass Ratio($μ$)

Abstract

Based on the spectroscopic constants derived from highly accurate potential energy surfaces, the SeD radical is identified as a spectroscopic probe for measuring spatial and temporal variation of fundamental physical constants such as the fine-structure constant (denoted as $α=\frac{e^2}{\hbar c}$) and the proton-to-electron mass ratio (denoted as $μ=\frac{m_p}{m_e}$). The ground state of SeD ($X^2Π$), due to spin-orbit coupling, splits into two fine structure multiplets $^2Π_{\frac{3}{2}}$ and $^2Π_{\frac{1}{2}}$. The potential energy surfaces of these spin-orbit components are derived from a state of the art electronic structure method, MRCI+Q inclusive of scalar relativistic effects with the spin-orbit effects accounted through the Breit-Pauli operator. The relevant spectroscopic data are evaluated using Murrel-Sorbie fit to the potential energy surfaces. The spin-orbit splitting($ω_f$) between the two multiplets is similar in magnitude with the harmonic frequency ($ω_e$) of the diatomic molecule. The amplification factor derived from this theoretical method for this particular molecule can be as large as 350, on the lower side it can be about 34. The significantly large values of K indicate that SeD radical can be a plaussible experimental candidate for measuring variation in $α$ and $μ$.