Fluorescence-enhanced second harmonic normal Raman scattering in β-carotene

β-carotene, an important biomolecule from the carotenoid family, plays a vital role in biosystem, the characteristic features of electronic and vibrational spectra will shed light on its photophysical properties. Here, in-situ high pressure Raman spectra of β-carotene are measured up to 26 GPa. Two possible phase transitions are identified at about 7 GPa and 14 GPa, respectively, through analysis of the frequency-pressure relationships. In order to clarify the intensity changes of Raman bands, high pressure UV–Vis absorption measurements of β-carotene are conducted. Besides resonance Raman enhancement effect, a new mechanism, fluorescence enhancement of normal Raman scattering, is proposed, which provides new methods and approaches for Raman spectroscopy. [Display omitted] •In-situ high pressure Raman spectra of β-carotene have been measured up to 26 Gpa.•Two possible phase transitions are detected at about 7 Gpa and 14 Gpa from the frequency-pressure relationships.•High pressure UV–Vis absorption spectra of β-carotene crystal are obtained for the first time.•A new mechanism, fluorescence enhancement of normal Raman scattering, is proposed.