Phase Shift Cavity Ring-Down (PS-CRD) Absorption of Esters in the Near-Infrared and Visible Regions: Agricultural Detection and Environmental Implications

Abstract

Highlights: What are the main findings? Optical pathlengths of 25 km are achieved with our PS-CRD technique. Absorption coefficients as low as 10−10 cm−1 are measured. What is the implication of the main finding? Vibrational overtones of organic esters are recorded. Emissions of esters in the field can be detected and identified by the CRD technique. A detailed description of the components of the CRD technique is presented and applied to the detection of organic esters. These molecules typically have a pleasant smell resembling the aroma of flowers and fruits and are responsible for many distinct odors in plants. They are emitted into the atmosphere by natural sources and human production. The weak absorption spectrum of the fifth vibrational overtone of ethyl, ethyl trimethyl, and tert-butyl acetate are recorded to show the sensitivity of the CRD technique. A description of a compact instrument to be used in the near-IR and visible regions will be presented for measurements of ester detection in the field. Potential chemical reactions of esters induced by visible light absorption in the atmosphere are discussed.