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the Im χ$_{0}$ ( q , ω ). Interestingly, if we move slightly away from M (on the edges of the volcano structure discussed above), we recover a linear trend starting at ω = 0. 

The band decomposition of Im χ$_{0}$ ( q , ω ), reported in Fig. 8 along the Γ − M − Γ line, shows that the inter-band ( e − h ) contributions dominate the high frequency part, and are also responsible for the low frequency peak around M . The two dispersive peaks at low frequency discussed above originate from the intra-band transitions ( e − e and h − h ); in particular, the relatively high frequency branch comes mainly from electronic bands, while the low frequency one from hole bands. Fig. 8 clearly shows that the h − h and e − e contributions are quite asymmetric; this asymmetry is clearly a consequence of the richness of the electronic structure of LaOFeAs near E$_{F}$ . 

