Hyperspectral stimulated Raman scattering microscopy is deployed to measure single-membrane vibrational spectrum as a function of membrane potential. Using erythrocyte ghost as a model, quantitative correlation between transmembrane potential and Raman spectral profile was found. Specifically, the ratio between the area under Raman band at $2930 cm À1 and that at $2850 cm À1 increased by $2.6 times when the potential across the erythrocyte ghost membrane varied from þ10 mV to À10 mV. Our results show the feasibility of employing stimulated Raman scattering microscopy to probe the membrane potential without labeling. V

Highly lignified vascular plant cell walls represent the majority of cellulosic biomass. Complete release of the biomass to deliver renewable energy by physical, chemical, and biological pretreatments is challenging due to the "protection" provided by polymerized lignin, and as such, additional tools to monitor lignin deposition and removal during plant growth and biomass deconstruction would be of great value. We developed a hyperspectral stimulated Raman scattering microscope with 9 cm(-1) spectral resolution and submicrometer spatial resolution. Using this platform, we mapped the aromatic ring of lignin, aldehyde, and alcohol groups in lignified plant cell walls. By multivariate curve resolution of the hyperspectral images, we uncovered a spatially distinct distribution of aldehyde and alcohol groups in the thickened secondary cell wall. These results collectively contribute to a deeper understanding of lignin chemical composition in the plant cell wall.

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Experimental investigation of laser-induced quadrupole-quadrupole collisional energy transfer between Xe and Kr is reported in this paper. The excitation spectrum of laser-induced collisional energy transfer (LICET) is characterized by a slowly decreasing tail on the blue side of the peak and a width of ∼30 cm −1 . The experimental evidence shows that in the quasistatic wing the quadrupole-quadrupole LICET spectrum follows a power law that is different from the dipole-dipole LICET line shape and the profile of the quadrupole-quadrupole LICET decreases more slowly than the dipole-dipole LICET profile. The results indicate that the laser-induced quadrupole-quadrupole collision can be considered as a practical process to transfer energy selectively from a storage state making a parity-nonallowed transition to a target state making a parity-allowed transition.

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