Feature and type Wavelength Assignment Reference
(i) 1730 nm (AF) CR1 : 1600–1815 nm
: not defined 1650/1669 nm 2υ 3 of aromatic CH stretch [5 , 7 ] ≈ 1700 nm2υ of CH stretch [34 ] 1706/1754 nm 2υ of CH, alkyl doublet [7 ] 1706 nm 4υ of aliphatic CH stretch [7 ] 1726 nm 2υ of aliphatic CH stretch [5 ] 1761/1769 nm 2υ of aliphatic CH stretch [5 ] 1730–1852 nm 4υ of methyl CH [7 ] (ii) 2330 nm (AF) CR: 2240–2410 nm
: 2330 nm 2275/2279 nm 3υ of CH2 , CH3 [5 , 7 ] ≈ 2300 nmυ + υ 4 of CH stretch[34 ] 2307–2469 nm 3υ of methyl CH stretch [7 ] 2309 nm 3υ of aliphatic CH stretch [5 ] 2331 nm 3υ of CH2 , COO [5 ] 2337/2386 nm 3υ of COO, CH3 [5 ] 2347 nm 3υ of aliphatic CH stretch [5 ] 2381 nm 3υ of CO stretch of carbohydrates [7 ] (iii) 450–740 nm (HF)
Decrease in reflectance in the visible range (e.g., [4 –6 , 35 ]) (iv) 1460–1750 nm (HF)
Decrease in reflectance in the near to shortwave infrared range (e.g., [4 , 6 , 35 ]) Iron oxides (i) 550 nm (AF) CR: 450–680 nm
: 550 nm ≈ 490 nmET5 band of Fe3+ [7 , 36 ] 503 nm Goethite [37 ] ≈ 510 nmET band of Fe2+ [36 , 38 ] 529 nm ET band of hematite [7 ] 535 nm Hematite [37 ] ≈ 550 nmET band of Fe2+ , hematite (e.g., [36 , 38 , 39 ]) (ii) 700 nm (AF) CR: 580–800 nm
: 700 nm 650 nm ET band of hematite and goethite [7 , 39 ] 665 nm ET band of goethite [37 ] 700 nm 4υ of O–H [7 ] ≈ 700 nmET band of Fe3+ (e.g., [35 , 36 , 38 ]) (iii) 900 nm (AF) CR: 750–1300 nm
: 870 nm ≈ 850–870 nmET band of hematite [39 , 40 ] 860 nm ET band of Fe2+ and Fe3+ [34 ] 868 nm Hematite [37 ] ≈ 870 nmET band of Fe3+ [35 , 36 , 38 ] 884 nm ET band of hematite [7 ] ≈ 900 nmTransition bands of Fe2+ and Fe3+ (e.g., [34 , 38 ]) 900–930 nm ET band of goethite [39 ] 920 nm ET band of goethite [7 ] ≈ 930 nm3υ of O–H stretch, Goethite [7 , 37 , 40 ] 940 nm υ + υ of O–H stretch[7 ] 1000–1100 nm ET band of Fe2+ (e.g., [35 , 36 ]) 1025 nm ET band of Fe3+ [8 ] 1075 nm ET band of Fe3+ [8 ] (iv) 550–590 nm (CF)
Decrease in reflectance in the blue wavelength range towards the ultraviolet light (e.g., [34 , 38 , 39 ]) (v) 450–750 nm (HF)
Decrease in reflectance in the visible range (e.g., [34 , 38 , 39 ]) Clay (i) 2200 nm (AF) CR: 2100–2290 nm
: 2206 nm 2160/216 + 2208/2209 nm δ
6 of AlOH bend of kaolinite doublet and υ + υ of OH stretch[7 , 37 , 50 ] ≈ 2200 nmδ of AlOH bend and υ + υ of OH stretch of montmorillonite and illite(e.g., [35 , 40 , 50 , 51 ]) 2200/2204 nm Montmorillonite [37 ] 2206 nm υ of OH stretch of montmorillonite and illite[7 ] 2208 nm δ of AlOH bend of kaolinite doublet[7 ] 2216 nm Illite [37 ] 2230 nm δ of AlOH bend of smectites[7 ] (ii) 2340 nm (AF) CR: 2270–2410 nm
: 2340 nm 2308/2312 nm Kaolinite [37 ] 2336 nm Illite [37 ] 2340 nm υ of OH stretch of illite(e.g., [7 , 22 , 50 ]) 2372/2376 nm Kaolinite [37 ] (iii) 450–700 nm (HF)
Increase in reflectance in the visible range (e.g., [34 , 42 ]) (iv) 1460–1750 nm (HF)
Increase in reflectance in the near to shortwave infrared range (e.g., [34 , 42 ])