Observation of a midinfrared fine-structure transition for the single trapped barium ion

Abstract

We report observation of laser excitation of a narrow, magnetic-dipole-allowed, infrared transition in a single trapped ion. Quantum jumps of a ${\mathrm{Ba}}^{+}$ atom were observed using a diode laser tuned in resonance with the excited-state 5d ${}_{}{}^2{}_{}{}^{}$ ${\mathit{D}}_{3/2}$–5d ${}_{}{}^2{}_{}{}^{}$ ${\mathit{D}}_{5/2}$ transition at 12.48 μm. Single-ion resonance line shapes were obtained and a transition frequency of ν=24 012 033±11 MHz was determined. Calculated quantum jump rates of the D-D transition for the applied laser spectral brightness yield agreement with experimentally observed values.