Modeling aerosol transmission spectra from n(λ) and k(λ) infrared optical constants measurements of organic liquids and solids.

The effects of light scattering and refraction play significantly different roles for aerosols than for bulk materials, making it challenging to identify aerosolized chemicals using traditional spectral methods or spectral reference libraries. Due to a potentially infinite number of particle morphologies, sizes, and compositions, constructing a database of laboratory-measured aerosol spectra is not a practical solution. Here, as an alternative approach, the measured n/k optical vectors of two example organic materials (diethyl phthalate and D-mannitol) are used in combination with particle absorption / scattering theory (Mie theory and FDTD) and the Beer-Lambert law to generate a series of synthetic infrared transmission / scattered light spectra.

Twice-Modulated Light in Fourier Transform Infrared (FT-IR) Spectrometers from Reflective Samples: Avoiding Distorted Intensity Values.

We document an artifact associated with the back reflection from samples or sampling accessories in Fourier transform spectrometers. Samples oriented normal to the incoming modulated beam can reflect light back to the interferometer and this light (the percentage dependent on the sample's refractive index) is modulated by the interferometer a second time resulting in light erroneously appearing at twice its true frequency. The phenomenon occurs across the spectrum but is most apparent when positive-going narrow absorption peaks at 1 display as negative-going peaks at 2.

Regiospecific Vinyl Phosphate/beta-Keto Phosphonate Rearrangements Initiated by Halogen-Metal Exchange.

A new strategy has been developed for preparation of beta-keto phosphonates via a halogen-metal exchange induced 1,3-phosphorus migration of 2-bromovinyl phosphates. These intermediates can be prepared through conversion of an alpha-bromo ketone to the appropriate enolate by reaction with strong base, or through conjugate addition to an alpha-bromo alpha,beta-unsaturated ketone. In either case, trapping the resulting enolate by reaction with a dialkyl phosphorochloridate gives the 2-bromovinyl phosphate.