Erratum: “Azide–water intermolecular coupling measured by two-color two-dimensional infrared spectroscopy” [J. Chem. Phys. 136, 224503 (2012)]

After publication of Ref. 1, it has been brought to our attention that Hochstrasser and co-workers have studied essentially the same molecular system (i.e.,

$N3−$ in H₂O instead of D₂O) by two-color 2D IR spectroscopy before us.² A cross peak is also observed, which less likely is due to population transfer because of the even larger energy gap from the

${\rm N}_3^-$

$N3−$ asymmetric stretch vibration to the H₂O band. We had based our conclusion, that population transfer is the dominant coupling mechanism, mostly on the large frequency separation of the 0-1 and the 1-2 transition in the 2D IR spectra, which reflects the large anharmonicity of the OD vibrator itself.¹ The 1-2 transition is not shown in Ref. 2, so we cannot decide whether an alternative coupling mechanism might be responsible for the cross-peak between

${\rm N}_3^-$

$N3−$ in H₂O. Nonetheless, Ref. 2 found a tilt in the cross-peak, evidencing a correlation in the vibrational frequencies the of

${\rm N}_3^-$

$N3−$ and the H₂O vibrations, which is another consequence of the coupling to azide-bound water.