Low-Frequency Raman Scattering in Colliding Benzene Droplets

Abstract

Low-frequency intermolecular motions are of importance for understanding the structure of molecular liquids, which can be elucidated by Raman spectroscopy. A liquid droplet provides a field where stimulated Raman scattering (SRS) readily proceeds. Our previous study showed that multiorder SRS is more effectively generated in colliding droplets than a single droplet. Here we report that the multiorder SRS generated in colliding benzene droplets included lowfrequency bands of the liquid benzene, which is considered to represent a temporal state of liquid emerging in the course of the droplet collision. This method enables measurements of the low-frequency intermolecular motions of the novel liquid state emerging at the mixed region of the colliding droplet without suffering from background of Rayleigh scattering.

Intramolecular Vibration Energy-Transfer-Driven Cascaded Stimulated Raman Scattering and Four-Wave Mixing in Benzene Series

“…The 1002 and 3066 cm –1 origins of the two series are assigned to bands of ring skeleton and CH stretching modes, respectively. The peaks with 1002 cm –1 intervals after the 1002 cm –1 origin were multiorder ring skeleton Stokes SRS, where the intense Stokes SRS excited the next Raman bands sequentially . The peaks were labeled as [ l m ], where l and m represent the number of the CC ring skeleton and CH stretching modes, respectively, in the multiorder Stokes SRS.…”

“…In Figure f, an additional peak appears at 5064 cm –1 , and the Raman shift is assigned to 5132 cm –1 . The side bands could be interpreted as SRS that included an intermolecular vibrational band . In addition, the sixth-order Stokes and third-order anti-Stokes SRS of the ring skeleton was also obtained.…”

“…It expands the physical mechanism of coherent light radiation and was usually used to study molecular structures and interactions. − SRS was used to generate cascaded Raman effect and realize wide-band excitation light sources. − The spectrum of SRS was determined by the maximum Raman scattering gain factor, depending on the Raman scattering cross section (RSCS) of the material. In typical SRS, only the most intensive Raman band was enhanced and observed, and the frequency-shift values (in units of cm –1 ) of SRS were determined by the strongest Raman transition modes of the chosen scattering media. − When the laser intensity was slightly higher than the SRS threshold, the first-order Stokes line can be created. With the increase in pump laser energy, the intense Raman scattered light excited the next Raman bands sequentially, and the second-order and higher-order Stokes SRS can be generated. − …”

“…The peaks with 1002 cm −1 intervals after the 1002 cm −1 origin were multiorder ring skeleton Stokes SRS, where the intense Stokes SRS excited the next Raman bands sequentially. 10 The peaks were labeled as [lm], where l and m represent the number of the CC ring skeleton and CH stretching modes, respectively, in the multiorder Stokes SRS. These assignments were confirmed with measurements using chlorobenzene.…”

“…The side bands could be interpreted as SRS that included an intermolecular vibrational band. 10 In addition, the sixth-order Stokes and third-order anti-Stokes SRS of the ring skeleton was also obtained. The energy transfer within the chlorobenzene molecule and the multiorder crossing excitation between CC and CH modes were formed, resulting in the 15-order cascaded SRS generation whose radiation bandwidth was from 458.5 to 789 nm.…”