Full text loading...
(Color online) Schematic of the single-beam CARS setup (a) and modified pulse shaper with typical before and after spectra (b). Pol.: Polarizer; SPF: short pass filter; blue double arrows indicate polarization of spectrum components. Delay stage in probe arm of shaper is not shown.
(Color online) CARS spectra acquired at 1 m standoff on <5 μm PS films (a), <2.5 μm PMMA films (b), and 200 nm PMMA film containing 10% DNT (c). Percentages refer to the concentration of 2,4DNT in the film relative to polymer mass. Unprocessed (a) and processed spectra (b) show detection of the 1350 cm−1 DNT feature at 2% concentration. Unprocessed spectra in (c) shows signal from a blank substrate (bottom spectrum) and 200 nm film (middle) integrated for 100 s to clarify features in the low signal to noise 1 s exposure (top). CO2 and the ro-vibrational features of O2 are also visible in (c).
(Color online) Stand-off chemical images created at 1 m. Title on each chemical image refers to the resonance monitored: PS = 1200 cm−1, DNT = 1350 cm−1, PMMA = 1750 cm−1, and 2,6-DNT = 1090 cm−1. Three types of samples in (a) show trace detection in a complex environment, 1: PS fingerprint on wafer; 2: two drops of PS on aluminum substrate ∼100 μm thick; 3: 3 μm PMMA film with half containing DNT. Residual toluene makes the PMMA film visible in the PS panel. The final panel reveals trace amount of DNT (one PS drop at 20% and half of the PMMA film at 2%). Three ∼3 μm films in (b) show isomer discrimination, 1: pure PS; 2: 2,6-DNT in PS at 20%; and 3: 2,4-DNT in PS at 20% concentration. Images were individually normalized and some are displayed saturated to emphasize small signals. Image dimensions: (a) 50 × 100 pixels and (b) 50 × 50 pixels.
(Color online) Standoff chemical images created at 1 m using selective excitation. The two intensity maps were created with 2 separate scans with 0.5 s of accumulation per pixel. The title refers to the selectively excited resonance: PS = 1200 cm−1 and DNT = 1350 cm−1. Only the corner of the 5 μm film contains DNT (40% concentration). Image dimensions: 40 × 40 pixels.
Article metrics loading...