Double-resonance spectroscopy determines highly excited vibrational energy of 13CO2 with kilohertz accuracy.
We present a comb-referenced mid-infrared to near-infrared double-resonance (MIR-NIR DR) scheme applied to 13CO2 to achieve high-accuracy rovibrational term values for highly excited, optically dark vibrational states. A single-pass MIR pump drives the strong ν3 = 1 ← 0 fundamental transition, while a cavity-enhanced N...