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1. Revisiting with Updated Hardware an Old Spectroscopic Technique: Circularly Polarized Luminescenceand
2. Molecular Iodine Fluorescence Spectra Generated with Helium-Neon Lasers for Spectrometer Calibration
Volume 64, Number 12 (Dec. 2010) Page 1416-1422
1. ETTORE CASTIGLIONI,* SERGIO ABBATE, and GIOVANNA LONGHI
2. J. CHARLES WILLIAMSON
1. Among the various chiroptical spectroscopic techniques available today, circularly polarized luminescence (CPL) plays a minor role and is still used by a limited number of specialists. The cost of the few commercial instruments available and the complexity of homemade apparatuses have strongly limited the widespread application of this technique. New technological approaches, such as the use of light-emitting diode (LED) sources, may significantly simplify the required instrumentation and encourage new potential users. Calibration procedure and the quantitative determination of CPL and total luminescence intensity as well as the corresponding g ratio are described.
Index Headings: Circularly polarized luminescence; CPL; Camphorquinone; Light-emitting diodes; LEDs.and
2. Gas-phase molecular iodine laser-induced fluorescence (LIF) spectra were recorded out to 815 nm at 1 cm-1 resolution using green, yellow, and red helium-neon (HeNe) lasers as excitation sources. Nine previously unreported I2 B←X absorption transitions accessed by these lasers were identified, and specific rovibronic transition assignments were made for two hundred LIF peaks—more than sixty per laser. These I2 LIF peaks can be used to calibrate the vacuum wavenumber coordinate of spectrometers to better than 0.1 cm-1 accuracy. In particular, green HeNe excitation of the I2 R(106) 28-0 transition leads to strong fluorescence well suited for calibration, with a rotational doublet spacing of 15 cm-1 and a doublet-to-doublet spacing of 190 cm-1. Calibration by HeNe I2 LIF may be an especially valuable technique for Raman spectroscopy applications.
Index Headings: Spectrometer calibration; Charge-coupled device; CCD; Molecular iodine; Laser-induced fluorescence; LIF; Helium-neon laser; Raman spectroscopy.