Desorption rate curves from the integrated absorbtion bands of pure HNCO (full squares) and HNCO for a HNCO:H₂O mixture where H₂O is in excess (crosses) and where H₂O is not in excess (full circles). The dotted lines are the results from the fits using a first-order desorption rate (Eq. (3)). Inset: OCN⁻ (triangles) desorption curve in a HNCO:H₂O mixture where H₂O is not in a 1:5 concentration ratio. Only the first part of the desorption curve is fitted, corresponding to the desorption of OCN⁻ alone.