\[Eta][l_, p_, \[Gamma]_] :=
2^(Abs[l] + 2)*
p!*(Abs[l] + p)!*\[Gamma]^2*(Sum[((-2)^
m Gamma[m + Abs[l]/2 +
1])/((p - m)! (Abs[l] + m)! m! (1 + \[Gamma]^2)^(
m + Abs[l]/2 + 1)), {m, 0, p}])^2
\[CapitalEta][l_, L_, p_, \[Gamma]_] := \[Eta][l, p, \[Gamma]]*1/(
4 Pi^2)*Abs[-I/(l - L) (Exp[I*2 Pi*(l - L)] - 1)]^2
DiscretePlot3D[\[CapitalEta][l, 1.2, p, 1/Sqrt[2]], {l, -3, 3}, {p, 0,
5}, ExtentSize -> Full]
DiscretePlot3D[\[CapitalEta][l, 1.2, p, 1/Sqrt[2]], {l, -3, 3}, {p, 0,
5}, ExtentSize -> Full, ScalingFunctions -> {None, None, "Log"}]
2^(Abs[l] + 2)*
p!*(Abs[l] + p)!*\[Gamma]^2*(Sum[((-2)^
m Gamma[m + Abs[l]/2 +
1])/((p - m)! (Abs[l] + m)! m! (1 + \[Gamma]^2)^(
m + Abs[l]/2 + 1)), {m, 0, p}])^2
\[CapitalEta][l_, L_, p_, \[Gamma]_] := \[Eta][l, p, \[Gamma]]*1/(
4 Pi^2)*Abs[-I/(l - L) (Exp[I*2 Pi*(l - L)] - 1)]^2
DiscretePlot3D[\[CapitalEta][l, 1.2, p, 1/Sqrt[2]], {l, -3, 3}, {p, 0,
5}, ExtentSize -> Full]
DiscretePlot3D[\[CapitalEta][l, 1.2, p, 1/Sqrt[2]], {l, -3, 3}, {p, 0,
5}, ExtentSize -> Full, ScalingFunctions -> {None, None, "Log"}]