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.