What absorbs at 797 cm⁻¹ in an FTIR spectrum?

Quick answer

A band near 797 cm⁻¹ is usually interpreted by checking which functional groups repeatedly co-occur there in the literature, then confirming at least one or two additional peaks in the same sample. This page ranks those assignments by accumulated evidence rather than by a single fixed textbook rule.

Possible functional-group assignments

Ranking reflects accumulated literature evidence, not a single authoritative rule. Always confirm against your sample context.

Possible materials

Materials are shown only when the same literature pool supports this band and at least one additional characteristic peak.

Spectrum logic

This band becomes meaningful only when read with its neighboring peaks. In practice, analysts first look at the assignments above, then check whether the same sample also shows other peaks expected for the same structural motif. A lone band near 797 cm⁻¹ is usually not enough for material identification by itself.

Real-world usage

This type of query is common in polymer identification, unknown plastic screening, QC troubleshooting, recycled-material verification, and literature-backed peak assignment review.

Common mistakes

• Treating one isolated band as proof of a material without checking at least one or two supporting peaks.
• Ignoring overlap: multiple functional groups can contribute near the same wavenumber.
• Skipping validation when additives, blends, oxidation, or contamination may distort the spectrum.

Verification advice

When ambiguity remains, validate the hypothesis with DSC, GC-MS, or TGA, especially for blends, degraded samples, and filled polymers.

Literature behind these assignments

• Water (H2O) confidence 1.0

  “Inthespectralregion1250-400cm-1ofsoilsfromintermediateBh the spectra of horizon Bh and Bhs, with the exception of the peak at cm-1, 1160 andBhshorizons(Fig.1),wherethemineralphasesKOandTOappear, which disappears due to the very low content”

  Clabel 等 - 2020 - Organo-mineral associations in a Spodosol from nor DOI: 10.1016/j.geodrs.2020.e00303
• Silicon-oxygen (Si-O) confidence 1.0

  “it holds the major lattice peaks of SiO at 797, 695, 450, and 2 However, this region may overlap with SOM bands (Table 2) as well as with a priori unknown bands of clay minerals and smectite/illite con-”

  FTIR photoacoustic spectroscopy for identification and assessment of soil components_ Chernozems and their size fractions DOI: 10.1016/j.pacs.2020.100162
• Silicon carbon confidence 1.0

  “film caused by defects and impurities in the diamond For A, cm(cid:1)1 the strong sharp absorptionpeak at 797 is due to SiC formed film at the interface of the due to low diamond nucleation density because no substrate surface pretreatment”

  Effect of methane concentration in hydrogen plasma on hydrogen impurity incorporation in thick large-grained polycrystalline diamond films DOI: 10.1016/j.jcrysgro.2015.06.018
• confidence 1.0

  “The FTIR spectra of unheated samples (Li-Mt0, Na-Mt0 and Cu-Mt0) showed that there were obvious absorption bands near cm-1, cm-1 cm-1 797 844 and 912 (Figure 3A-C), which presumably correspond to the OH Minerals2022,12,477”

  Thermal Migration Behavior of Na+, Cu2+ and Li+in Montmorillonite DOI: 10.3390/min12040477
• confidence 1.0

  “cm-1 cm-1, 1605 and 3383-3601 being assigned to the vibrational modes of the deformation IR bands of PTA situated at 523 cm-1, 594 cm-1, 797 cm-1, 891 cm-1, 982 cm-1, 1080 cm-1, 1605 (O corresponds to corner oxygen atoms), W-O e-W stretchin”

  The Photoluminescence and Vibrational Properties of Black Phosphorous Sheets Chemically/Electrochemically Functionalized in the Presence of Diphenylamine DOI: 10.3390/polym14214479
• Silicon (Si) confidence 1.0

  “The weak absorption band at 797 cm-1 is related to the vibration of the symmetric stretching of the Si-O-Si bonds [37,38].”

  Study of Geopolymer Composites Based on Volcanic Ash, Fly Ash, Pozzolan, Metakaolin and Mining Tailing DOI: 10.3390/buildings12081118
• confidence 1.0

  “The FTIR spectrum registered on raw umber from Cyprus (sample PK40610) highlights (PK11100 and PK11010) could indicate a high Fe content in the octahedral sheet, possibly the presence of goethite (characteristic peaks at 3190, 898 and 797 c”

  Assessment of Easily Accessible Spectroscopic Techniques Coupled with Multivariate Analysis for the Qualitative Characterization and Differentiation of Earth Pigments of Various Provenance DOI: 10.3390/min12060755
• Silicon carbon confidence 1.0

  “The peak at 797 corresponds SiC, while the peak 1060 corresponds to SiO 2.”

  Criner 等 - 2018 - Quantification of Material State using Reflectance DOI: 10.1063/1.5031610