Laser heating of sulfuric acid droplets held in air by laser Raman tweezers

Abstract

An optical trap is used to hold a droplet of concentrated sulfuric acid in the focus of Ar-ion laser (l = 514.5 nm). The temperature and concentration of sulfuric acid in the droplet is calculated from the shifts and intensities of the Stokes-shifted Raman bands around 1000 rel.cm 21 . Aqueous sulfuric acid droplets can thus be used as a 'thermometer' for optically trapped droplets in air. It is demonstrated that the laser power can be kept low enough to prevent significant laser heating of the trapped droplet and that high laser powers (in excess of 16 mW) can result in heating of 5-10 uC.

The reaction of oleic acid monolayers with gas-phase ozone at the air water interface: the effect of sub-phase viscosity, and inert secondary components

“…2). A laser trapped [67][68][69] droplet of oleic acid and synthetic seawater being oxidised by gas-phase ozone demonstrates a stationary point in the decay of oleic acid as followed by Raman spectroscopy, and rise of the reaction product nonanoic acid. The timing of the stationary point coincides with the completion of droplet growth by water absorption from the ambient air.…”

Determining the unique refractive index properties of solid polystyrene aerosol using broadband Mie scattering from optically trapped beads

“…The technique provides a contact free method of studying single aerosol particles and is an ideal way to model aerosols in the climate and their related atmospheric chemistry. 19,20 Optical trapping is suitable for the analysis of laboratory generated aerosol but is, to our knowledge, untested against atmospheric aerosol sources. Complications may arise for particles that strongly absorb light at the laser trapping wavelength.…”

Evaluation of time-gated Raman spectroscopy for the determination of nitric, sulfuric and hydrofluoric acid concentrations in pickle liquor

“…11 These findings are in agreement with previous reports. [9][10][11][12] Linear dependence between the intensity of Raman scattering and concentration was observed for both HNO3 and H2SO4. Although the responses seemed linear even when analyzing solutions containing both HNO3 and H2SO4, sulfuric acid produces some Raman scattering (HSO4 -(ν3) and (ν4) modes) at the HNO3 1042 cm -1 wavenumber region.…”

“…Although the responses seemed linear even when analyzing solutions containing both HNO3 and H2SO4, sulfuric acid produces some Raman scattering (HSO4 -(ν3) and (ν4) modes) at the HNO3 1042 cm -1 wavenumber region. 9,10,12,13 Hence a multivariate model might be a more suitable data analysis method in part because of this (discussed more in depth later). Any Raman peaks correlating with sample HF concentration were not observed with the time-gated Raman spectrometer used.…”