Light sources, broadband

Light source (broadband slits smaller than X) ... 

Light sources can either be broadband, such as a Globar, a Nemst glower, an incandescent wire or mercury arc lamp or they can be tunable, such as a laser or optical parametric oscillator (OPO). In the fomier case, a monocln-omator is needed to achieve spectral resolution. In the case of a tunable light source, the spectral resolution is detemiined by the linewidth of the source itself In either case, the spectral coverage of the light source imposes limits on the vibrational frequencies that can be measured. Of course, limitations on the dispersing element and detector also affect the overall spectral response of the spectrometer. 

Two scans are required to obtain an absorption spectrum. First, a blank reference scan is taken that characterizes the broadband light source. Then a scan with the sample in place is recorded. The ratio of the sample power spectrum to the reference power spectrum is the transmission spectrum. If the source has stable output, then a single reference scan can be used with many sample scans. 

A8, which leads to D, = 1/(2A8). The factor of two arises because a minimum of two data points per period are needed to sample a sinusoidal wavefonn. Naturally, the broadband light source will detennine the actual content of the spectrum, but it is important that the step size be small enough to acconunodate the highest frequency components of the source, otherwise they... 

Most optical spectral measurements, where the measurement of multiple wavelengths is required, will feature some type of polychromatic or broadband light source. There are a few exceptions here, such as tunable laser sources and source arrays. In such instances, the source is effectively "monochromatic at a given point in time. These sources are covered separately under monochromatic sources. 

Most optical spectral measurements, where the measurement of multiple wavelengths is required, will feature some type of polychromatic or broadband light source. There are a... 

A mid-infrared absorption instrument generally consists of a Fourier transform design with the same basic components as noted above for the Fourier transform near-infrared spectrometers (broadband light source, Michelson interferometer, and detector optimized for the mid-infrared spectral region.)... 

The second building block is the illumination unit. Depending on the application, broadband light sources ranging from LEDs to specially modified kW-floodlights may be used. The light sources must provide an even, stable illumination of the sample, as shadows or other inhomogeneities in illumination may lead, for example, to erroneous classification results. 

When excited with a broadband (white light) source, Au nanoparticles will scatter light at the resonance frequency corresponding to Aspr, often giving rise to a brilliant iridescence. In most cases, the nanoparticle is much smaller than Aspr, such... 

---