Editing Infrared spectroscopy (section)

=== Other methods in molecular vibrational spectroscopy ===
Infrared spectroscopy is not the only method of studying molecular vibrational spectra. [[Raman spectroscopy]] involves an [[inelastic scattering]] process in which only part of the energy of an incident photon is absorbed by the molecule, and the remaining part is scattered and detected. The energy difference corresponds to absorbed vibrational energy.{{citation needed|date=February 2024}}

The [[selection rule]]s for infrared and for Raman spectroscopy are different at least for some [[molecular symmetry|molecular symmetries]], so that the two methods are complementary in that they observe vibrations of different symmetries.{{citation needed|date=February 2024}}

Another method is [[electron energy loss spectroscopy]] (EELS), in which the energy absorbed is provided by an inelastically scattered electron rather than a photon. This method is useful for studying vibrations of molecules [[Adsorption|adsorbed]] on a solid surface.

Recently, [[High resolution electron energy loss spectroscopy|high-resolution EELS]] (HREELS) has emerged as a technique for performing vibrational spectroscopy in a [[Transmission electron microscopy|transmission electron microscope]] (TEM).<ref name=":0">{{cite journal | vauthors = Krivanek OL, Lovejoy TC, Dellby N, Aoki T, Carpenter RW, Rez P, Soignard E, Zhu J, Batson PE, Lagos MJ, Egerton RF, Crozier PA | display-authors = 6 | title = Vibrational spectroscopy in the electron microscope | journal = Nature | volume = 514 | issue = 7521 | pages = 209–12 | date = October 2014 | pmid = 25297434 | doi = 10.1038/nature13870 | bibcode = 2014Natur.514..209K | s2cid = 4467249 }}</ref> In combination with the high spatial resolution of the TEM, unprecedented experiments have been performed, such as nano-scale temperature measurements,<ref>{{cite journal | vauthors = Idrobo JC, Lupini AR, Feng T, Unocic RR, Walden FS, Gardiner DS, Lovejoy TC, Dellby N, Pantelides ST, Krivanek OL | display-authors = 6 | title = Temperature Measurement by a Nanoscale Electron Probe Using Energy Gain and Loss Spectroscopy | journal = Physical Review Letters | volume = 120 | issue = 9 | pages = 095901 | date = March 2018 | pmid = 29547334 | doi = 10.1103/PhysRevLett.120.095901 | bibcode = 2018PhRvL.120i5901I | doi-access = free }}</ref><ref>{{cite journal | vauthors = Lagos MJ, Batson PE | title = Thermometry with Subnanometer Resolution in the Electron Microscope Using the Principle of Detailed Balancing | journal = Nano Letters | volume = 18 | issue = 7 | pages = 4556–4563 | date = July 2018 | pmid = 29874456 | doi = 10.1021/acs.nanolett.8b01791 | bibcode = 2018NanoL..18.4556L | s2cid = 206748146 }}</ref> mapping of isotopically labeled molecules,<ref>{{cite journal | vauthors = Hachtel JA, Huang J, Popovs I, Jansone-Popova S, Keum JK, Jakowski J, Lovejoy TC, Dellby N, Krivanek OL, Idrobo JC | display-authors = 6 | title = Identification of site-specific isotopic labels by vibrational spectroscopy in the electron microscope | journal = Science | volume = 363 | issue = 6426 | pages = 525–528 | date = February 2019 | pmid = 30705191 | doi = 10.1126/science.aav5845 | bibcode = 2019Sci...363..525H | doi-access = free }}</ref> mapping of phonon modes in position- and momentum-space,<ref>{{cite journal | vauthors = Hage FS, Nicholls RJ, Yates JR, McCulloch DG, Lovejoy TC, Dellby N, Krivanek OL, Refson K, Ramasse QM | display-authors = 6 | title = Nanoscale momentum-resolved vibrational spectroscopy | journal = Science Advances | volume = 4 | issue = 6 | pages = eaar7495 | date = June 2018 | pmid = 29951584 | pmc = 6018998 | doi = 10.1126/sciadv.aar7495 | bibcode = 2018SciA....4.7495H }}</ref><ref>{{cite journal | vauthors = Senga R, Suenaga K, Barone P, Morishita S, Mauri F, Pichler T | title = Position and momentum mapping of vibrations in graphene nanostructures | journal = Nature | volume = 573 | issue = 7773 | pages = 247–250 | date = September 2019 | pmid = 31406319 | doi = 10.1038/s41586-019-1477-8 | arxiv = 1812.08294 | bibcode = 2019Natur.573..247S | s2cid = 118999071 }}</ref> vibrational surface and bulk mode mapping on nanocubes,<ref>{{cite journal | vauthors = Lagos MJ, Trügler A, Hohenester U, Batson PE | title = Mapping vibrational surface and bulk modes in a single nanocube | journal = Nature | volume = 543 | issue = 7646 | pages = 529–532 | date = March 2017 | pmid = 28332537 | doi = 10.1038/nature21699 | bibcode = 2017Natur.543..529L | s2cid = 4459728 }}</ref> and investigations of [[polariton]] modes in van der Waals crystals.<ref>{{cite journal | vauthors = Govyadinov AA, Konečná A, Chuvilin A, Vélez S, Dolado I, Nikitin AY, Lopatin S, Casanova F, Hueso LE, Aizpurua J, Hillenbrand R | display-authors = 6 | title = Probing low-energy hyperbolic polaritons in van der Waals crystals with an electron microscope | journal = Nature Communications | volume = 8 | issue = 1 | pages = 95 | date = July 2017 | pmid = 28733660 | pmc = 5522439 | doi = 10.1038/s41467-017-00056-y | arxiv = 1611.05371 | bibcode = 2017NatCo...8...95G }}</ref>
Analysis of vibrational modes that are IR-inactive but appear in [[inelastic neutron scattering]] is also possible at high spatial resolution using EELS.<ref>{{cite journal| vauthors = Venkatraman K, Levin BD, March K, Rez P, Crozier PA |date=2019|title=Vibrational spectroscopy at atomic resolution with electron impact scattering |journal=Nature Physics|volume=15|issue=12|pages=1237–1241 |doi=10.1038/s41567-019-0675-5 |arxiv=1812.08895|bibcode=2019NatPh..15.1237V|s2cid=119452520}}</ref> Although the spatial resolution of HREELs is very high, the bands are extremely broad compared to other techniques.<ref name=":0" />