Schematic diagram of the levitator (A–F), second stage optics (G), and process chamber. Ultrasonic sound waves are generated by the piezoelectric transducer (E). Owing to multiple reflections between the transducer and the concave reflector (D), a standing wave is generated. A micrometer (A) allows the distance between the front plate of the transducer and the reflector to be adjusted to an integral number of half wavelengths. The pressure amplitude of the standing wave is monitored by connecting the output of the piezoelectric sensor (C) via connector (B) to an oscilloscope. The RF power to the transducer is input via connector F. For clarity, the supports for the levitator and second stage optics are not shown.
Top view of the levitator apparatus displaying the ultrasonic levitator, process chamber, carbon dioxide laser, Raman spectrometer, FTIR spectrometer, IR detector, and the first stage optics. The inset shows the levitator including the supports in more detail.
Alteration in the Raman spectrum when a grain of gypsum (CaSO4·2H2O) levitated in anhydrous nitrogen is dehydrated to anhydrite (CaSO4) by irradiation from a CO2 laser. The assignments of the ν(SO4) and ν(H2O) vibrational modes for the gypsum peaks are shown. The corresponding ν1(SO4) and ν3(SO4) vibrational modes in anhydrite are observed at slightly higher Raman shifts (see text for details).
Possible reaction pathways for linking two L-cysteine molecules when heated.
Raman spectrum of a levitated L-cysteine sample before and after irradiation by the CO2 laser (top) compared with a reference D-cystine Raman spectrum (bottom). Following irradiation, a new peak appears due to the ν(S–S) stretch mode, and the ν(C–C) and ν(C–S) stretch mode peaks move to higher Raman shifts (see top figure). The unirradiated cysteine peak assignments 33 are a(CCNbend), b(CO2 rock), c(CH2 rock), d(CO2 wagg), e(CCstr), f(SHbend), g(NH3 rock), and h(NH3 rock). The label 1 refers to a peak not clearly present in either the unirradiated L-cysteine or cystine (see text for details). The cystine peak assignments shown are from Ref. 34 .
Raman spectrum of a levitated L-cysteine sample in the 1650–1080 cm−1 range before (top spectrum) and after irradiation (bottom spectrum) by the CO2 laser. The unirradiated cysteine peak assignments, 33 where available, are a(CHbend), b(CH2 twist), c(CH rock), d(CH2 wagg), e(NH3 sym. bend), f(CO2 sym.), g(CH2 bend), h(NH3 asym. bend), i(NH3 asym. bend), and j(CO2 asym. str.). For illustration purposes, the unirradiated spectrum is shown displaced vertically upwards.
Raman spectrum showing the E2g and A1g modes 37 of grain of graphite levitated in oxygen.
FTIR spectrum of a 38 μm thick, levitated polystyrene sheet (top) compared to standard spectrum from the same material (bottom). The assignments 38 of selected, prominent vibrational modes are shown (see text for details).
FTIR spectrum of a levitated polyethylene sheet (top) compared to standard spectrum from the same material (bottom). The assignments 39 of the vibrational modes are shown (see the text for details).
FTIR spectrum of levitated expanded polystyrene (top) compared to a standard polystyrene spectrum (bottom). The assignments 38 of selected, prominent vibrational modes are shown (see text for details).
Temperature, T p , of a 1 mm diameter gypsum particle levitated in nitrogen at atmospheric pressure as a function of the CO2 laser power.
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