Fig. 3. (a) Resonance Raman spectra of the azide adduct of (i) met-WT with Na¹⁴N₃, (ii) met-I119H with Na¹⁴N₃, (iii) met-I119H with Na¹⁵N₃, and (iv) the difference spectrum ¹⁵N₃ minus ¹⁴N₃ adducts of met-I119H. Peaks are labeled according to their vibrational assignments, as described in the text. (b) FTIR spectra of the azide adduct of (i) met-WT at 5 K, (ii) met-I119H at 5 K, and (iii) met-I119H at 25 °C.