Research Article
Raman Study on Pompeii Potteries: The Role of Calcium Hydroxide on the Surface Treatment
Table 2
(a) Fundamental vibrational modes of the carbonates according to [
3,
4]. (b) Raman bands in some carbonates and hydroxyl-carbonates.
(a) |
| Mode | Symmetry | Selection rules | Frequencies (cm−1) |
|
Nondegenerate symmetric stretch | A′1 | Raman | 1064 | Nondegenerate asymmetric (out of plane) bend | A′′2 | IR | Near 800 | Doubly degenerate asymmetric stretch | E′ | IR + Raman | 1415 | Doubly degenerate symmetric (in-plane) bend | E′ | IR + Raman | 680 |
|
|
(b) |
| Calcite [5, 6] | Siderite [7, 8] | Aragonite [9–11] | Strontianite [10, 12] | Vaterite [13] | Azurite [7, 14] | Free [15, 16] | Assignment [15, 16] |
| 89 | | | | | 112 | | R (CO3) |
| 162 | 190 | | | 212 | 165 194 | | T (Ca, CO3) |
| 288 | 294 | 284 | 246 | 287 | 281 | | T (Ca, CO3) |
| | 506 | | | | 540 | | T (Ca, Fe, CO3) |
| 716 | 731 742 | 701 705 | 701 711 | 750 | 739 764 | 680 |
4-Symmetric CO3 bending mode |
| | | 853 | 855 | | 815 835 | 879 |
2-Asymmetric CO3 bending mode |
| | | | | | 937 952 | | O–H out-of-plane bending mode |
| 1092 | 1087 | 1085 | 1074 | 1090 | 1095 | 1063 |
1-Symmetric CO3 stretching mode |
| 1437 | | 1465 1547 | 1408 1447 | 1441 | 1421 1431 1462 | 1415 |
3-Asymmetric CO3 stretching mode |
| | | | | | 1582 | | O–H bending mode |
| 1754 | 1726 1733 | | | | | |
1 + 4 |
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|