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Infrared spectroscopy (IR spectroscopy or vibrational spectroscopy) is the measurement of the interaction of infrared radiation with matter by absorption, emission, or reflection. It is used to study and identify chemical substances or functional groups in solid, liquid, or gaseous forms.
Fourier transform infrared spectroscopy (FTIR) [1] is a technique used to obtain an infrared spectrum of absorption or emission of a solid, liquid, or gas. An FTIR spectrometer simultaneously collects high-resolution spectral data over a wide spectral range.
The spectral resolution of a spectrograph, or, more generally, of a frequency spectrum, is a measure of its ability to resolve features in the electromagnetic spectrum.It is usually denoted by , and is closely related to the resolving power of the spectrograph, defined as =, where is the smallest difference in wavelengths that can be distinguished at a wavelength of .
AFM-IR enables nanoscale infrared spectroscopy, [52] i.e. the ability to obtain infrared absorption spectra from nanoscale regions of a sample. Chemical compositional mapping AFM-IR can also be used to perform chemical imaging or compositional mapping with spatial resolution down to ~10-20 nm, [ 18 ] limited only by the radius of the AFM tip.
Recording infrared spectra as a function of position can be used for nanoscale mapping of the sample chemical composition, [4] [5] performing a local ultrafast IR spectroscopy [6] and analyzing the nanoscale intermolecular coupling, [7] among others. A spatial resolution of 10 nm to 20 nm is routinely achieved. [4]
Particularly in nano-FTIR, where the scattering from a sharp probe-tip is used to perform spectroscopy of samples with nanoscale spatial resolution, a high-power illumination from pulsed infrared lasers makes up for a relatively small scattering efficiency (often < 1%) of the probe.
An ATR accessory for IR spectroscopy. ATR uses a property of total internal reflection resulting in an evanescent wave. A beam of infrared light is passed through the ATR crystal in such a way that it reflects at least once off the internal surface in contact with the sample. This reflection forms the evanescent wave which extends into the sample.
The end of the Dark Ages – first light and re-ionization: [3] Near-infrared spectroscopy (NIRS) at spectral resolutions around 100 and 1000 for studying the first light sources (stars, galaxies and active nuclei) that mark the beginning of the phase of re-ionization of the Universe that is believed to take place between redshifts 15–14 and 6.
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