The absorption spectrum of Ln3+ is normally sharp and weak in intensity. However, Sm3+ (4f5 ) in dil acidic solution shows a broad and moderately intense transition at 495nm. This transition is
1
6H5/2 → 6H7/2
2
6H5/2 → 4G5/2
3
6H5/2 → 6H9/2
4
4G5/2 → 4G7/2