Production of ${\mathrm{YbH}}^{+}$ by chemical reaction of ${\mathrm{Yb}}^{+}$ in excited states with ${\mathrm{H}}_2$ gas

It is known that fluorescence of trapped ${\mathrm{Yb}}^{+}$ ions fades with continuous driving of the ${}_{}{}^2{}_{}{}^{}$ ${\mathrm{S}}_{1\mathrm{/}2}$ ${\mathrm{-}}^2$ ${\mathrm{P}}_{1\mathrm{/}2}$ transition in the presence of buffer gases. This phenomenon has been interpreted as being caused by population trapping in the ${}_{}{}^2{}_{}{}^{}$ ${\mathrm{F}}_{7\mathrm{/}2}$ state of ${\mathrm{Yb}}^{+}$ . As another cause of the fluorescence disappearance, we found the production of ${\mathrm{YbH}}^{+}$ by chemical reaction of ${\mathrm{Yb}}^{+}$ in excited states with ${\mathrm{H}}_2$ gas. We found that the wavelengths of 369.482, 369.202, and 368.947 nm, formerly assigned as wavelengths for deexcitation of ${\mathrm{Yb}}^{+}$ in the ${}_{}{}^2{}_{}{}^{}$ ${\mathrm{F}}_{7\mathrm{/}2}$ state to the ${}_{}{}^2{}_{}{}^{}$ ${\mathrm{S}}_{1\mathrm{/}2}$ ground state, are actually photodissociation lines of ${\mathrm{YbH}}^{+}$ . The change of the resonance point of rf resonance absorption signals indicates the production and dissociation of ${\mathrm{YbH}}^{+}$ ions. The production of ${\mathrm{YbH}}^{+}$ may be a problem in establishing frequency standards using buffer-gas-cooled ${\mathrm{Yb}}^{+}$ , owing to difficulty in removing ${\mathrm{H}}_2$ gas from vacuum systems.