Ultralow frequency Stokes and anti-Stokes Raman spectroscopy of single living cells and microparticles using a hot rubidium vapor filter.

We report on ultralow frequency Stokes and anti-Stokes Raman spectroscopy of single living cells and microsized particles in an aqueous medium with a frequency shift down to 10 cm(-1) by the combination of a hot rubidium (Rb) vapor filter, a confocal pinhole, and optical trapping. A single frequency-stabilized diode laser beam at 780.2 nm is used to optically trap and excite a single living cell or microparticle, and the Rayleigh scattering light from the particle is effectively blocked with a Rb vapor cell and a confocal pinhole. Ultralow frequency Raman spectra of the trapped cells or microparticles in both Stokes and anti-Stokes regions are then measured with a single-stage CCD spectrograph.