  Super-high resolution laser-based angle-resolved photoemission spectroscopy
measurements have been carried out on a heavily overdoped (Bi,Pb)2Sr2CuO6 (Tc>
5 K) superconductor. Taking advantage of the high-precision data on the subtle
change of the quasi-particle dispersion at different temperatures, we develop a
general procedure to determine the bare band dispersion and extract the bosonic
spectral function quantitatively. Our results show unambiguously that the 70
meV nodal kink is due to the electron coupling with the multiple phonon modes,
with a large mass enhancement factor Lamda= 0.42 even in the heavily over-doped
regime.
