Electronic spectroscopy of a cold SiO$^+$ sample: Implications for optical pumping

The dispersed fluorescence following pulsed dye laser excitation of the $\textrm{B}_2 \Sigma^+ - \textrm{X}^2 \Sigma^+(0,0)$ band of a cold sample of SiO$^+$ has been recorded and analyzed. The branching ratios for $\textrm{B}_2 \Sigma^+ (v=0) \rightarrow \textrm{X}^2 \Sigma^+(v)$ and $\textrm{B}_2 \Sigma^+ (v=0) \rightarrow \textrm{A}^2 \Pi_i(v)$ emission were determined and compared with values predicted based upon existing experimental and theoretical data. The experimentally determined branching ratios show that the $\textrm{B}_2 \Sigma^+ (v=0) \rightarrow \textrm{X}^2 \Sigma^+(v)$ transitions are somewhat less diagonal than predicted. The implications for laser cooling of a trapped sample of SiO$^+$ using broadband laser excitation are discussed.