SPECTROSCOPY IN SUPPORT OF PARITY NONCONSERVATION MEASURMENTS: THE $A^{2}$$\Pi-X^{2}\Sigma^{+}$ (0,0) BAND OF BARIUM MONFLUORIDE

Abstract

There is renewed interest in the spectroscopy of heavy metal containing polar radical diatomic molecules because they provide a sensitive venue for detection of parity nonconservation (PNC) either from the determination of the electric dipole moment (EDM) {\textbf{56} } R3326, 1997.} of the electron, \textit{d$_{e}$}, or detection of the interaction of the anapole moment of the nuclei with the unpaired electron {\textbf{100}} 023003, 2008.}. The effects due to \textit{d$_{e}$} are nuclear spin independent and studies of both the even and odd nuclear spin isotopologues are relevant. Recently, DeMille \textit{et al} proposed using an odd isotopologue of barium monofluoride, $^{137}BaF$, to measure the nuclear spin-dependent parity non-conservation (NSD-PNC) effect resulting from the interaction of the anapole moment of $^{137}Ba$ with the unpaired electron of the $X^{2}\Sigma^{+}$ electronic state. Here we report on the analysis of the field-free spectrum of the $A^{2}$$\Pi-X^{2}\Sigma^{+}$(0,0) band of $^{137}BaF$ and an analysis of the $^{137}Ba(I=3/2)$ and $^{19}F(I=1/2)$ hyperfine interaction in the $A^{2}$$\Pi$ state. The hyperfine interaction in the $X^{2}\Sigma^{+}$ state has been previously characterized from the analysis of the pure rotation spectrum. {\textbf{71}} 389, 1982.} The optimal optical transitions for monitoring $^{137}BaF$ in future PNC measurements will be discussed.