Squared form factors of vibronic excitations in 12-13.3 eV of nitrogen studied by high-resolution inelastic x-ray scattering

Vibronically resolved squared form factors of a a ''(1)Sigma(+)(g), b(1)Pi(u), b' (1)Sigma(+)(u), c(3) (1)Pi(u), c(4)' (1)Sigma(+)(u), and o(3) (1)Pi(u) of molecular nitrogen are determined by inelastic x-ray scattering with a high resolution of 70 meV. Through a comparison with the previous results measured by electron energy loss spectroscopy, it is found that the first Born approximation is satisfied at an incident electron energy of 300 eV in the small momentum transfer region for a dipole-allowed transition of b(1)Pi(u), but the first Born approximation is not reached at an impact energy of 500 eV for the dipole-forbidden transition of a ''(1)Sigma(+)(g). It is also observed from the present experimental results that the momentum transfer dependence behavior of the excitations to b(1)Pi(u) (nu' = 3,4) is different from that of the excitations to b(1)Pi(u) (nu' = 1,2), which can be attributed to the perturbation of c(3) (1)Pi(u) to b(1)Pi(u). The present results provide experimental benchmark data of inelastic squared form factors of molecular nitrogen.