4.5 μm diode laser spectrum of (HI)2

The 4.5 μm infrared spectrum of (HI)2 has been recorded using a supersonic jet diode laser spectrometer. The spectrum assigned to the ν2+ band is interpreted as being associated with a ground state rotational constant, B0=378.438(50) MHz, corresponding distortion constant, DJ0=0.402(20) kHz, band origin, ν0(ν2+)=2217.30262(7) cm−1 and a Rcm distance of 4.563(2) Å. Combination bands originating from the ground state are assigned with ν0=2234.75157(6) cm−1 and ν0=2233.65326(9) cm−1 respectively. Observed spectra are consistent with the tunneling dynamics for other members of the homologous series (HX)2, X=Cl and Br.