Synthesis and surface spectroscopy of α-pinene isotopologues and their corresponding secondary organic material.

Atmospheric aerosol-cloud interactions remain among the least understood processes within the climate system, leaving large uncertainties in the prediction of future climates. In particular, the nature of the surfaces of aerosol particles formed from biogenic terpenes, such as α-pinene, is poorly understood despite the importance of surface phenomena in their formation, growth, radiative properties, and ultimate fate. Herein we report the coupling of a site-specific deuterium labeling strategy with vibrational sum frequency generation (SFG) spectroscopy to probe the surface C-H oscillators in α-pinene-derived secondary organic aerosol material (SOM) generated in an atmospheric flow tube reactor.

Vibrational Mode Assignment of α-Pinene by Isotope Editing: One Down, Seventy-One To Go.

This study aims to reliably assign the vibrational sum frequency generation (SFG) spectrum of α-pinene at the vapor/solid interface using a method involving deuteration of various methyl groups. The synthesis of five deuterated isotopologues of α-pinene is presented to determine the impact that removing contributions from methyl group C-H oscillators has on its SFG response. 0.

Accurate line shapes from sub-1 cm(-1) resolution sum frequency generation vibrational spectroscopy of α-pinene at room temperature.

Despite the importance of terpenes in biology, the environment, and catalysis, their vibrational spectra remain unassigned. Here, we present subwavenumber high-resolution broad-band sum frequency generation (HR-BB-SFG) spectra of the common terpene (+)-α-pinene that reveal 10 peaks in the C-H stretching region at room temperature. The high spectral resolution resulted in spectra with more and better resolved spectral features than those of the Fourier transform infrared, femtosecond stimulated Raman spectra in the bulk condensed phase and those of the conventional BB-SFG and scanning SFG spectroscopy of the same molecule on a surface.

Vibrational sum frequency generation spectroscopy of secondary organic material produced by condensational growth from α-pinene ozonolysis.

Secondary organic material (SOM) was produced in a flow tube from α-pinene ozonolysis, and collected particles were analyzed spectroscopically via a nonlinear coherent vibrational spectroscopic technique, namely sum frequency generation (SFG). The SOM precursor α-pinene was injected into the flow tube reactor at concentrations ranging from 0.125 ± 0.

Size-resolved sea spray aerosol particles studied by vibrational sum frequency generation.

We present vibrational sum frequency generation (SFG) spectra of the external surfaces and the internal interfaces of size-selected sea spray aerosol (SSA) particles generated at the wave flume of the Scripps Hydraulics Laboratory. Our findings support SSA particle models that invoke the presence of surfactants in the topmost particle layer and indicate that the alkyl chains of surfactant-rich SSA particles are likely to be disordered. Specifically, the SFG spectra suggest that across the range of sizes studied, surfactant-rich SSA particles contain CH oscillators that are subject to molecular orientation distributions that are broader than the narrow molecular distribution functions associated with well-ordered and well-aligned alkyl chains.

Size-dependent changes in sea spray aerosol composition and properties with different seawater conditions.

A great deal of uncertainty exists regarding the chemical diversity of particles in sea spray aerosol (SSA), as well as the degree of mixing between inorganic and organic species in individual SSA particles. Therefore, in this study, single particle analysis was performed on SSA particles, integrating transmission electron microscopy with energy dispersive X-ray analysis and scanning transmission X-ray microscopy with near edge X-ray absorption fine structure spectroscopy, with a focus on quantifying the relative fractions of different particle types from 30 nm to 1 μm. SSA particles were produced from seawater in a unique ocean-atmosphere facility equipped with breaking waves.

Raman microspectroscopy and vibrational sum frequency generation spectroscopy as probes of the bulk and surface compositions of size-resolved sea spray aerosol particles.

Sea spray aerosol (SSA) represents one of the largest aerosol components in our atmosphere. SSA plays a major role in influencing climate; however the overall impacts remain poorly understood due to the overall chemical complexity. SSA is comprised of a mixture of inorganic and organic components in varying proportions that change as a function of particle size and seawater composition.

Organic constituents on the surfaces of aerosol particles from Southern Finland, Amazonia, and California studied by vibrational sum frequency generation.

This article summarizes and compares the analysis of the surfaces of natural aerosol particles from three different forest environments by vibrational sum frequency generation. The experiments were carried out directly on filter and impactor substrates, without the need for sample preconcentration, manipulation, or destruction. We discuss the important first steps leading to secondary organic aerosol (SOA) particle nucleation and growth from terpene oxidation by showing that, as viewed by coherent vibrational spectroscopy, the chemical composition of the surface region of aerosol particles having sizes of 1 μm and lower appears to be close to size-invariant.

On molecular chirality within naturally occurring secondary organic aerosol particles from the central Amazon Basin.

In this perspectives article, we reflect upon the existence of chirality in atmospheric aerosol particles. We then show that organic particles collected at a field site in the central Amazon Basin under pristine background conditions during the wet and dry seasons consist of chiral secondary organic material. We show how the chiral response from the aerosol particles can be imaged directly without the need for sample dissolution, solvent extraction, or sample preconcentration.