Eigenvalues of i sigma dot x

gamma0 = {{0,1},{1,0}};
gammai = {{0, sigmai}, {-sigmai, 0}};

gamma0.gammai // MatrixForm

(PauliMatrix[#] // MatrixForm) &/@ {1,2,3}
p = (PauliMatrix[#] ) &/@ {1,2,3};
i = IdentityMatrix[2];
q = I{i x,i y,i z};
iSigmaDotX = Total[p[[#]].q[[#]]&/@ {1,2,3}];
iSigmaDotX// MatrixForm
iSigmaDotX // Eigenvalues