Hyper‐Raman spectral signatures of structured and de‐structured hydrogen‐bonded water

Abstract Hyper‐Raman (HR) spectra of liquid water have been measured in the temperature range from 15 to 45°C. A total of 76 spectra obtained at an interval of about 0.5°C are analyzed by singular value decomposition (SVD) and multivariate curve resolution with alternate least squares (MCR‐ALS) analyses. Obtained temperature‐dependent HR spectra are univocally decomposed into two components, corresponding to de‐structured hydrogen‐bonded water (DH water) and structured hydrogen‐bonded water (SH water). The results are in complete agreement with those of Raman spectroscopy, supporting the understanding that SH water and DH water coexist in thermal equilibrium in ambient liquid water.