The case of ANL was experimentally revisited in the present work (see ESI † and Ref. for details), because there was a hypothesis of an anharmonic perturbation in place . The size-selected literature spectrum of the monohydrate of ANL 58 exhibits a very strong, partially saturated signal at 3524 cm -1 and a sharp satellite at 3547 cm -1 with unclear origin. To account for the possibility of an intensity stealing by this satellite, 3526 cm -1 with an uncertainty of ±3 cm -1 was proposed for the best deperturbed band position estimate . Comparison with the FTIR spectra in the present work confirms the main peak at 3525 cm -1 , i.e. within 1 cm -1 . It rules out a relative intensity of 10% or more for any weak satellite contribution near 3547 cm -1 . Therefore, the resonance hypothesis can be dropped and the new best estimate is 3525 cm -1 with an uncertainty of ±1 cm -1 , in line with the original raw result .