Abstract

Ammonia and eight aliphatic amines (ranging in alkyl chain length from <i>C</i><sub>1</sub> to <i>C</i><sub>16</sub>) are photolyzed at 193 nm, producing fluorescent molecular fragments (NH from ammonia; CN, CH, and NH from the amines). Fluorescence from NH is used to quantify ammonia; CN fluorescence is used to quantify the amines. Limits of detection in the 10-50 pmol regime, precision of ~6% RSD, and linear dynamic ranges of 1-3 decades in, quantity of parent compound are observed. A small but discernible "large molecule effect" exists; as the size of the alkyl chain in RNH<sub>2</sub> increases, the limit of detection increases, and the dependence of the fragment fluorescence signal on photolysis laser fluence also increases. Attempts to enhance fragment fluorescence intensities via "probe-laser" excitation of ground-state fragments were unsuccessful; it is inferred that, at the photolysis fluences employed (~2 × 10<sup>18</sup> photons/cm<sup>2</sup>), few ground-state fragments are formed.

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