Spectrochemistry is the application of spectroscopy in several fields of chemistry. It includes analysis of spectra in chemical terms, and use of spectra to derive the structure of chemical compounds, and also to qualitatively and quantitively analyze their presence in the sample. It is a method of chemical analysis that relies on the measurement of wavelengths and intensity of electromagnetic radiation . [1]
It was not until 1666 that Isaac Newton showed that white lights from the sun could be dissipated into a continuous series of colors. So Newton introduced the concept which he called spectrum to describe this phenomenon. He used a small aperture to define the beam of light, a lens to collimate it, a glass prism to disperse it, and a screen to display the resulting spectrum. Newton's analysis of light was the beginning of the science of spectroscopy. Later, It became clear that the Sun's radiation might have components outside the visible portion of the spectrum. In 1800 William Hershel showed that the sun's radiation extended into infrared, and in 1801 John Wilhelm Ritter also made a similar observation in the ultraviolet . Joseph Von Fraunhofer extended Newton's discovery by observing the sun's spectrum when sufficiently dispersed was blocked by a fine dark lines now known as Fraunhofer lines. Fraunhofer also developed diffracting grating, which disperses the lights in much the same way as does a glass prism but with some advantages. the grating applied interference of lights to produce diffraction provides a direct measuring of wavelengths of diffracted beams. So by extending Thomas Young's study which demonstrated that a light beam passes slit emerges in patterns of light and dark edges Fraunhofer was able to directly measure the wavelengths of spectral lines. However, despite his enormous achievements, Fraunhofer was unable to understand the origins of the special line in which he observed. It was not until 33 years after his passing that Gustav Kirchhoff established that each element and compound has its unique spectrum and that by studying the spectrum of an unknown source, one could determine its chemical compositions, and with these advancements, spectroscopy became a truly scientific method of analyzing the structures of chemical compounds. Therefore, by recognizing that each atom and molecule has its spectrum Kirchhoff and Robert Bunsen established spectroscopy as a scientific tool for probing atomic and molecular structures and founded the field of spectrochemical analysis for analyzing the composition of materials. [3]
IR Spectrum Table by Frequency [4]
Frequency Range | Absorption (cm−1) | Appearance | Group | Compound Class | Comments |
---|---|---|---|---|---|
4000–3000 cm−1 | 3700-3584 | medium, sharp | O-H stretching | alcohol | free |
3550-3200 | strong, broad | O-H stretching | alcohol | intermolecular bonded | |
3500 | medium | N-H stretching | primary amine | ||
3400 | |||||
3400-3300 | medium | N-H stretching | aliphatic primary amine | ||
3330-3250 | |||||
3350-3310 | medium | N-H stretching | secondary amine | ||
3300-2500 | strong, broad | O-H stretching | carboxylic acid | usually centered on 3000 cm−1 | |
3200-2700 | weak, broad | O-H stretching | alcohol | intramolecular bonded | |
3000-2800 | strong, broad | N-H stretching | amine salt | ||
3000–2500 cm−1 | |||||
3000–2500 cm−1 | 3333-3267 | strong, sharp | C-H stretching | alkyne | |
3100-3000 | medium | C-H stretching | alkene | ||
3000-2840 | medium | C-H stretching | alkane | ||
2830-2695 | medium | C-H stretching | aldehyde | doublet | |
2600-2550 | weak | S-H stretching | thiol | ||
2400–2000 cm−1 | |||||
2400–2000 cm−1 | 2349 | strong | O=C=O stretching | carbon dioxide | |
2275-2250 | strong, broad | N=C=O stretching | isocyanate | ||
2260-2222 | weak | CΞN stretching | nitrile | ||
2260-2190 | weak | CΞC stretching | alkyne | disubstituted | |
2175-2140 | strong | S-CΞN stretching | thiocyanate | ||
2160-2120 | strong | N=N=N stretching | azide | ||
2150 | C=C=O stretching | ketene | |||
2145-2120 | strong | N=C=N stretching | carbodiimide | ||
2140-2100 | weak | CΞC stretching | alkyne | monosubstituted | |
2140-1990 | strong | N=C=S stretching | isothiocyanate | ||
2000-1900 | medium | C=C=C stretching | allene | ||
2000 | C=C=N stretching | ketenimine | |||
2000–1650 cm−1 | |||||
2000–1650 cm−1 | 2000-1650 | weak | C-H bending | aromatic compound | overtone |
1870-1540 | |||||
1818 | strong | C=O stretching | anhydride | ||
1750 | |||||
1815-1785 | strong | C=O stretching | acid halide | ||
1800-1770 | strong | C=O stretching | conjugated acid halide | ||
1775 | strong | C=O stretching | conjugated anhydride | ||
1720 | |||||
1770-1780 | strong | C=O stretching | vinyl / phenyl ester | ||
1760 | strong | C=O stretching | carboxylic acid | monomer | |
1750-1735 | strong | C=O stretching | esters | 6-membered lactone | |
1750-1735 | strong | C=O stretching | δ-lactone | γ: 1770 | |
1745 | strong | C=O stretching | cyclopentanone | ||
1740-1720 | strong | C=O stretching | aldehyde | ||
1730-1715 | strong | C=O stretching | α,β-unsaturated ester | or formates | |
1725-1705 | strong | C=O stretching | aliphatic ketone | or cyclohexanone or cyclopentenone | |
1720-1706 | strong | C=O stretching | carboxylic acid | dimer | |
1710-1680 | strong | C=O stretching | conjugated acid | dimer | |
1710-1685 | strong | C=O stretching | conjugated aldehyde | ||
1690 | strong | C=O stretching | primary amide | free (associated: 1650) | |
1690-1640 | medium | C=N stretching | imine / oxime | ||
1685-1666 | strong | C=O stretching | conjugated ketone | ||
1680 | strong | C=O stretching | secondary amide | free (associated: 1640) | |
1680 | strong | C=O stretching | tertiary amide | free (associated: 1630) | |
1650 | strong | C=O stretching | δ-lactam | γ: 1750-1700 β: 1760-1730 | |
1670–1600 cm−1 | |||||
1670–1600 cm−1 | 1678-1668 | weak | C=C stretching | alkene | disubstituted (trans) |
1675-1665 | weak | C=C stretching | alkene | trisubstituted | |
1675-1665 | weak | C=C stretching | alkene | tetrasubstituted | |
1662-1626 | medium | C=C stretching | alkene | disubstituted (cis) | |
1658-1648 | medium | C=C stretching | alkene | vinylidene | |
1650-1600 | medium | C=C stretching | conjugated alkene | ||
1650-1580 | medium | N-H bending | amine | ||
1650-1566 | medium | C=C stretching | cyclic alkene | ||
1648-1638 | strong | C=C stretching | alkene | monosubstituted | |
1620-1610 | strong | C=C stretching | α,β-unsaturated ketone | ||
1600–1300 cm−1 | |||||
1600–1300 cm−1 | 1550-1500 | strong | N-O stretching | nitro compound | |
1372-1290 | |||||
1465 | medium | C-H bending | alkane | methylene group | |
1450 | medium | C-H bending | alkane | methyl group | |
1375 | |||||
1390-1380 | medium | C-H bending | aldehyde | ||
1385-1380 | medium | C-H bending | alkane | gem dimethyl | |
1370-1365 | |||||
1400–1000 cm−1 | |||||
1400–1000 cm−1 | 1440-1395 | medium | O-H bending | carboxylic acid | |
1420-1330 | medium | O-H bending | alcohol | ||
1415-1380 | strong | S=O stretching | sulfate | ||
1200-1185 | |||||
1410-1380 | strong | S=O stretching | sulfonyl chloride | ||
1204-1177 | |||||
1400-1000 | strong | C-F stretching | fluoro compound | ||
1390-1310 | medium | O-H bending | phenol | ||
1372-1335 | strong | S=O stretching | sulfonate | ||
1195-1168 | |||||
1370-1335 | strong | S=O stretching | sulfonamide | ||
1170-1155 | |||||
1350-1342 | strong | S=O stretching | sulfonic acid | anhydrous | |
1165-1150 | hydrate: 1230-1120 | ||||
1350-1300 | strong | S=O stretching | sulfone | ||
1160-1120 | |||||
1342-1266 | strong | C-N stretching | aromatic amine | ||
1310-1250 | strong | C-O stretching | aromatic ester | ||
1275-1200 | strong | C-O stretching | alkyl aryl ether | ||
1075-1020 | |||||
1250-1020 | medium | C-N stretching | amine | ||
1225-1200 | strong | C-O stretching | vinyl ether | ||
1075-1020 | |||||
1210-1163 | strong | C-O stretching | ester | ||
1205-1124 | strong | C-O stretching | tertiary alcohol | ||
1150-1085 | strong | C-O stretching | aliphatic ether | ||
1124-1087 | strong | C-O stretching | secondary alcohol | ||
1085-1050 | strong | C-O stretching | primary alcohol | ||
1070-1030 | strong | S=O stretching | sulfoxide | ||
1050-1040 | strong, broad | CO-O-CO stretching | anhydride | ||
1000–650 cm−1 | |||||
1000–650 cm−1 | 995-985 | strong | C=C bending | alkene | monosubstituted |
915-905 | |||||
980-960 | strong | C=C bending | alkene | disubstituted (trans) | |
895-885 | strong | C=C bending | alkene | vinylidene | |
850-550 | strong | C-Cl stretching | halo compound | ||
840-790 | medium | C=C bending | alkene | trisubstituted | |
730-665 | strong | C=C bending | alkene | disubstituted (cis) | |
690-515 | strong | C-Br stretching | halo compound | ||
600-500 | strong | C-I stretching | halo compound | ||
900–700 cm−1 | |||||
900–700 cm−1 | 880 ± 20 | strong | C-H bending | 1,2,4-trisubstituted | |
810 ± 20 | |||||
880 ± 20 | strong | C-H bending | 1,3-disubstituted | ||
780 ± 20 | |||||
(700 ± 20) | |||||
810 ± 20 | strong | C-H bending | 1,4-disubstituted or | ||
1,2,3,4-tetrasubstituted | |||||
780 ± 20 | strong | C-H bending | 1,2,3-trisubstituted | ||
(700 ± 20) | |||||
755 ± 20 | strong | C-H bending | 1,2-disubstituted | ||
750 ± 20 | strong | C-H bending | monosubstituted | ||
700 ± 20 | benzene derivative |
IR Spectra Table by Compound Class [5]
Compound Class | Group | Absorption (cm−1) | Appearance | Comments |
---|---|---|---|---|
acid halide | C=O stretching | 1815-1785 | strong | |
alcohols | O-H stretching | 3700-3584 | medium, sharp | free |
O-H stretching | 3550-3200 | strong, broad | intermolecular bonded | |
O-H stretching | 3200-2700 | weak, broad | intramolecular bonded | |
O-H bending | 1420-1330 | medium | ||
aldehyde | C-H stretching | 2830-2695 | medium | doublet |
C=O stretching | 1740-1720 | strong | ||
C-H bending | 1390-1380 | medium | ||
aliphatic ether | C-O stretching | 1150-1085 | strong | |
aliphatic ketone | C=O stretching | 1725-1705 | strong | or cyclohexanone or cyclopentenone |
aliphatic primary amine | N-H stretching | 3400-3300 | medium | |
alkane | C-H stretching | 3000-2840 | medium | |
C-H bending | 1465 | medium | methylene group | |
C-H bending | 1450 | medium | methyl group | |
C-H bending | 1385-1380 | medium | gem dimethyl | |
C-H stretching | 3100-3000 | medium | ||
C=C stretching | 1678-1668 | weak | disubstituted (trans) | |
C=C stretching | 1675-1665 | weak | trisubstituted | |
C=C stretching | 1675-1665 | weak | tetrasubstituted | |
C=C stretching | 1662-1626 | medium | disubstituted (cis) | |
C=C stretching | 1658-1648 | medium | vinylidene | |
C=C stretching | 1648-1638 | strong | monosubstituted | |
C=C bending | 995-985 | strong | monosubstituted | |
C=C bending | 980-960 | strong | disubstituted (trans) | |
C=C bending | 895-885 | strong | vinylidene | |
C=C bending | 840-790 | medium | trisubstituted | |
C=C bending | 730-665 | strong | disubstituted (cis) | |
alkyl aryl ether | C-O stretching | 1275-1200 | strong | |
alkyne | C-H stretching | 3333-3267 | strong, sharp | |
CΞC stretching | 2260-2190 | weak | disubstituted | |
CΞC stretching | 2140-2100 | weak | monosubstituted | |
allene | C=C=C stretching | 2000-1900 | medium | |
amine | N-H bending | 1650-1580 | medium | |
C-N stretching | 1250-1020 | medium | ||
amine salt | N-H stretching | 3000-2800 | strong, broad | |
anhydride | C=O stretching | 1818 | strong | |
CO-O-CO stretching | 1050-1040 | strong, broad | ||
aromatic amine | C-N stretching | 1342-1266 | strong | |
aromatic compound | C-H bending | 2000-1650 | weak | overtone |
aromatic ester | C-O stretching | 1310-1250 | strong | |
azide | N=N=N stretching | 2160-2120 | strong | |
benzene derivative | 700 ± 20 | |||
carbodiimide | N=C=N stretching | 2145-2120 | strong | |
carbon dioxide | O=C=O stretching | 2349 | strong | |
carboxylic acid | O-H stretching | 3300-2500 | strong, broad | usually centered on 3000 cm−1 |
C=O stretching | 1760 | strong | monomer | |
C=O stretching | 1720-1706 | strong | dimer | |
O-H bending | 1440-1395 | medium | ||
conjugated acid | C=O stretching | 1710-1680 | strong | dimer |
conjugated acid halide | C=O stretching | 1800-1770 | strong | |
conjugated aldehyde | C=O stretching | 1710-1685 | strong | |
conjugated alkene | C=C stretching | 1650-1600 | medium | |
conjugated anhydride | C=O stretching | 1775 | strong | |
conjugated ketone | C=O stretching | 1685-1666 | strong | |
cyclic alkene | C=C stretching | 1650-1566 | medium | |
cyclopentanone | C=O stretching | 1745 | strong | |
ester | C-O stretching | 1210-1163 | strong | |
esters | C=O stretching | 1750-1735 | strong | 6-membered lactone |
fluoro compound | C-F stretching | 1400-1000 | strong | |
halo compound | C-Cl stretching | 850-550 | strong | |
C-Br stretching | 690-515 | strong | ||
C-I stretching | 600-500 | strong | ||
imine / oxime | C=N stretching | 1690-1640 | medium | |
isocyanate | N=C=O stretching | 2275-2250 | strong, broad | |
isothiocyanate | N=C=S stretching | 2140-1990 | strong | |
ketene | C=C=O stretching | 2150 | ||
ketenimine | C=C=N stretching | 2000 | ||
monosubstituted | C-H bending | 750 ± 20 | strong | |
nitrile | CΞN stretching | 2260-2222 | weak | |
nitro compound | N-O stretching | 1550-1500 | strong | |
none | 3330-3250 | |||
none | 1870-1540 | |||
none | 1750 | |||
none | 1720 | |||
none | 1372-1290 | |||
none | 1375 | |||
none | 1370-1365 | |||
none | 1200-1185 | |||
none | 1204-1177 | |||
none | 1195-1168 | |||
none | 1170-1155 | |||
none | 1165-1150 | hydrate: 1230-1120 | ||
none | 1160-1120 | |||
none | 1075-1020 | |||
none | 1075-1020 | |||
none | 915-905 | |||
none | 810 ± 20 | |||
none | 780 ± 20 | |||
none | (700 ± 20) | |||
none | (700 ± 20) | |||
phenol | O-H bending | 1390-1310 | medium | |
primary alcohol | C-O stretching | 1085-1050 | strong | |
primary amide | C=O stretching | 1690 | strong | free (associated: 1650) |
N-H stretching | 3500 | medium | ||
secondary alcohol | C-O stretching | 1124-1087 | strong | |
secondary amide | C=O stretching | 1680 | strong | free (associated: 1640) |
secondary amine | N-H stretching | 3350-3310 | medium | |
sulfate | S=O stretching | 1415-1380 | strong | |
sulfonamide | S=O stretching | 1370-1335 | strong | |
sulfonate | S=O stretching | 1372-1335 | strong | |
sulfone | S=O stretching | 1350-1300 | strong | |
sulfonic acid | S=O stretching | 1350-1342 | strong | anhydrous |
sulfonyl chloride | S=O stretching | 1410-1380 | strong | |
sulfoxide | S=O stretching | 1070-1030 | strong | |
tertiary alcohol | C-O stretching | 1205-1124 | strong | |
tertiary amide | C=O stretching | 1680 | strong | free (associated: 1630) |
thiocyanate | S-CΞN stretching | 2175-2140 | strong | |
thiol | S-H stretching | 2600-2550 | weak | |
vinyl / phenyl ester | C=O stretching | 1770-1780 | strong | |
vinyl ether | C-O stretching | 1225-1200 | strong | |
α,β-unsaturated ester | C=O stretching | 1730-1715 | strong | or formates |
α,β-unsaturated ketone | C=C stretching | 1620-1610 | strong | |
δ-lactam | C=O stretching | 1650 | strong | γ: 1750-1700 β: 1760-1730 |
δ-lactone | C=O stretching | 1750-1735 | strong | γ: 1770 |
1,2,3,4-tetrasubstituted | ||||
1,2,3-trisubstituted | C-H bending | 780 ± 20 | strong | |
C-H bending | 880 ± 20 | strong | ||
1,2-disubstituted | C-H bending | 755 ± 20 | strong | |
C-H bending | 880 ± 20 | strong | ||
1,4-disubstituted or | C-H bending | 810 ± 20 | strong |
To use an IR spectrum table, first need to find the frequency or compound in the first column, depending on which type of chart that is being used. Then find the corresponding values for absorption, appearance and other attributes. The value for absorption is usually in cm−1.
NOTE: NOT ALL FREQUENCIES HAVE A RELATED COMPOUND.
Invasive Ductal Carcinoma (IDC) is one of the common types of breast cancer which accounts for 8 out of 10 of all invasive breast cancers. According to the American Cancer Society, more than 180,000 women in the United States find out that they have breast cancers each year, and most are diagnosed with this specific type of cancer. [6] While it is essential to detect breast cancer early to reduce the death rate there may be already more than 10,000,000 cells in breast cancer when it can be observed by x-ray mammograms. however, the IR Spectrum proposed by Szu et al seems to be more promising in detecting breast cancer cells several months ahead of a mammogram. Clinical tests have been carried out with approval of Institutional Review Board of National Taiwan University Hospital. So from August 2007 to June 2008 35 patients aged between (30-66) with an average age of 49 were enlisted in this project. the results established that about 63% of the success rate could be achieved with the cross-sectional data. Therefore the results concluded that breast cancers may be detected more accurately by cross-referencing S1 maps of multiple three-points. [7]
A Lignin in plant cell is a complex amorphous polymer and it is biosynthesized from three aromatic alcohols, namely P-Coumaryl , Coniferyl , and Sinapyl alcohols. Lignin is a highly branched polymer and accounts for 15-30% by weight of lignocellulosic biomass (LCBM) , so the structure of lignin will vary significantly according to the type of LCBM and the composition will depend on the degradation process. [8] This biosynthesis process is mainly consists of radical coupling reactions and it generates a particular lignin polymer in each plant species. So due to having a complex structure, various molecular spectroscopic methods have been applied to resolve the aromatic units and different interunit linkages in lignin from distinct plant species. [9]
Infrared 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. It can be used to characterize new materials or identify and verify known and unknown samples. The method or technique of infrared spectroscopy is conducted with an instrument called an infrared spectrometer which produces an infrared spectrum. An IR spectrum can be visualized in a graph of infrared light absorbance on the vertical axis vs. frequency, wavenumber or wavelength on the horizontal axis. Typical units of wavenumber used in IR spectra are reciprocal centimeters, with the symbol cm−1. Units of IR wavelength are commonly given in micrometers, symbol μm, which are related to the wavenumber in a reciprocal way. A common laboratory instrument that uses this technique is a Fourier transform infrared (FTIR) spectrometer. Two-dimensional IR is also possible as discussed below.
Spectroscopy is the field of study that measures and interprets the electromagnetic spectra that result from the interaction between electromagnetic radiation and matter as a function of the wavelength or frequency of the radiation. Matter waves and acoustic waves can also be considered forms of radiative energy, and recently gravitational waves have been associated with a spectral signature in the context of the Laser Interferometer Gravitational-Wave Observatory (LIGO)
An optical spectrometer is an instrument used to measure properties of light over a specific portion of the electromagnetic spectrum, typically used in spectroscopic analysis to identify materials. The variable measured is most often the light's intensity but could also, for instance, be the polarization state. The independent variable is usually the wavelength of the light or a unit directly proportional to the photon energy, such as reciprocal centimeters or electron volts, which has a reciprocal relationship to wavelength.
A spectrum is a condition that is not limited to a specific set of values but can vary, without gaps, across a continuum. The word was first used scientifically in optics to describe the rainbow of colors in visible light after passing through a prism. As scientific understanding of light advanced, it came to apply to the entire electromagnetic spectrum. It thereby became a mapping of a range of magnitudes (wavelengths) to a range of qualities, which are the perceived "colors of the rainbow" and other properties which correspond to wavelengths that lie outside of the visible light spectrum.
UV spectroscopy or UV–visible spectrophotometry refers to absorption spectroscopy or reflectance spectroscopy in part of the ultraviolet and the full, adjacent visible regions of the electromagnetic spectrum. Being relatively inexpensive and easily implemented, this methodology is widely used in diverse applied and fundamental applications. The only requirement is that the sample absorb in the UV-Vis region, i.e. be a chromophore. Absorption spectroscopy is complementary to fluorescence spectroscopy. Parameters of interest, besides the wavelength of measurement, are absorbance (A) or transmittance (%T) or reflectance (%R), and its change with time.
Astrochemistry is the study of the abundance and reactions of molecules in the Universe, and their interaction with radiation. The discipline is an overlap of astronomy and chemistry. The word "astrochemistry" may be applied to both the Solar System and the interstellar medium. The study of the abundance of elements and isotope ratios in Solar System objects, such as meteorites, is also called cosmochemistry, while the study of interstellar atoms and molecules and their interaction with radiation is sometimes called molecular astrophysics. The formation, atomic and chemical composition, evolution and fate of molecular gas clouds is of special interest, because it is from these clouds that solar systems form.
The emission spectrum of a chemical element or chemical compound is the spectrum of frequencies of electromagnetic radiation emitted due to an electron making a transition from a high energy state to a lower energy state. The photon energy of the emitted photon is equal to the energy difference between the two states. There are many possible electron transitions for each atom, and each transition has a specific energy difference. This collection of different transitions, leading to different radiated wavelengths, make up an emission spectrum. Each element's emission spectrum is unique. Therefore, spectroscopy can be used to identify elements in matter of unknown composition. Similarly, the emission spectra of molecules can be used in chemical analysis of substances.
Absorption spectroscopy refers to spectroscopic techniques that measure the absorption of radiation, as a function of frequency or wavelength, due to its interaction with a sample. The sample absorbs energy, i.e., photons, from the radiating field. The intensity of the absorption varies as a function of frequency, and this variation is the absorption spectrum. Absorption spectroscopy is performed across the electromagnetic spectrum.
A chemical structure determination includes a chemist's specifying the molecular geometry and, when feasible and necessary, the electronic structure of the target molecule or other solid. Molecular geometry refers to the spatial arrangement of atoms in a molecule and the chemical bonds that hold the atoms together, and can be represented using structural formulae and by molecular models; complete electronic structure descriptions include specifying the occupation of a molecule's molecular orbitals. Structure determination can be applied to a range of targets from very simple molecules, to very complex ones.
Near-infrared spectroscopy (NIRS) is a spectroscopic method that uses the near-infrared region of the electromagnetic spectrum. Typical applications include medical and physiological diagnostics and research including blood sugar, pulse oximetry, functional neuroimaging, sports medicine, elite sports training, ergonomics, rehabilitation, neonatal research, brain computer interface, urology, and neurology. There are also applications in other areas as well such as pharmaceutical, food and agrochemical quality control, atmospheric chemistry, combustion research and astronomy.
Extended X-ray absorption fine structure (EXAFS), along with X-ray absorption near edge structure (XANES), is a subset of X-ray absorption spectroscopy (XAS). Like other absorption spectroscopies, XAS techniques follow Beer's law. The X-ray absorption coefficient of a material as a function of energy is obtained using X-rays of a narrow energy resolution are directed at a sample and the incident and transmitted x-ray intensity is recorded as the incident x-ray energy is incremented.
Resonance Raman spectroscopy is a Raman spectroscopy technique in which the incident photon energy is close in energy to an electronic transition of a compound or material under examination. The frequency coincidence can lead to greatly enhanced intensity of the Raman scattering, which facilitates the study of chemical compounds present at low concentrations.
Matrix isolation is an experimental technique used in chemistry and physics. It generally involves a material being trapped within an unreactive matrix. A host matrix is a continuous solid phase in which guest particles are embedded. The guest is said to be isolated within the host matrix. Initially the term matrix-isolation was used to describe the placing of a chemical species in any unreactive material, often polymers or resins, but more recently has referred specifically to gases in low-temperature solids. A typical matrix isolation experiment involves a guest sample being diluted in the gas phase with the host material, usually a noble gas or nitrogen. This mixture is then deposited on a window that is cooled to below the melting point of the host gas. The sample may then be studied using various spectroscopic procedures.
The chemical state of a chemical element is due to its electronic, chemical and physical properties as it exists in combination with itself or a group of one or more other elements. A chemical state is often defined as an "oxidation state" when referring to metal cations. When referring to organic materials, a chemical state is usually defined as a chemical group, which is a group of several elements bonded together. Material scientists, solid state physicists, analytical chemists, surface scientists and spectroscopists describe or characterize the chemical, physical and/or electronic nature of the surface or the bulk regions of a material as having or existing as one or more chemical states.
In chemistry and molecular physics, fluxionalmolecules are molecules that undergo dynamics such that some or all of their atoms interchange between symmetry-equivalent positions. Because virtually all molecules are fluxional in some respects, e.g. bond rotations in most organic compounds, the term fluxional depends on the context and the method used to assess the dynamics. Often, a molecule is considered fluxional if its spectroscopic signature exhibits line-broadening due to chemical exchange. In some cases, where the rates are slow, fluxionality is not detected spectroscopically, but by isotopic labeling and other methods.
Chemical imaging is the analytical capability to create a visual image of components distribution from simultaneous measurement of spectra and spatial, time information. Hyperspectral imaging measures contiguous spectral bands, as opposed to multispectral imaging which measures spaced spectral bands.
Vibrational circular dichroism (VCD) is a spectroscopic technique which detects differences in attenuation of left and right circularly polarized light passing through a sample. It is the extension of circular dichroism spectroscopy into the infrared and near infrared ranges.
Medullary breast carcinoma is a rare type of breast cancer that is characterized as a relatively circumscribed tumor with pushing, rather than infiltrating, margins. It is histologically characterized as poorly differentiated cells with abundant cytoplasm and pleomorphic high grade vesicular nuclei. It involves lymphocytic infiltration in and around the tumor and can appear to be brown in appearance with necrosis and hemorrhage. Prognosis is measured through staging but can often be treated successfully and has a better prognosis than other infiltrating breast carcinomas.
Modern spectroscopy in the Western world started in the 17th century. New designs in optics, specifically prisms, enabled systematic observations of the solar spectrum. Isaac Newton first applied the word spectrum to describe the rainbow of colors that combine to form white light. During the early 1800s, Joseph von Fraunhofer conducted experiments with dispersive spectrometers that enabled spectroscopy to become a more precise and quantitative scientific technique. Since then, spectroscopy has played and continues to play a significant role in chemistry, physics and astronomy. Fraunhofer observed and measured dark lines in the Sun's spectrum, which now bear his name although several of them were observed earlier by Wollaston.
The infrared Ca II triplet, commonly known as the calcium triplet, is a triplet of three ionised calcium spectral lines at the wavelengths of 8498 Å, 8542 Å and 8662 Å. The triplet has a strong emission, and is most prominently observed in the absorption of spectral type G, K and M stars.
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