Relativistic Doppler effect invisible ultraviolet wavelengths, infrared light is blueshifted into the visible range. Precisely what changes in the colors one sees depends on the physiology of the human eye and on the spectral characteristics of the light sources being observed. The Doppler effect (with arbitrary direction) also modifies the perceived source intensity: this can be expressed concisely by the fact that source strength divided by the cube of the frequency is a Lorentz invariant This implies that the total radiant intensity (summing over all frequencies) is multiplied by the fourth power of the Doppler factor for frequency. As a consequence, since Planck's
Ultraviolet photoelectron spectroscopy seen a considerable revival with the increasing availability of synchrotron light sources which provide a wide range of monochromatic photon energies. Ultraviolet photoelectron spectroscopy Ultraviolet photoelectron spectroscopy (UPS) refers to the measurement of kinetic energy spectra of photoelectrons emitted by molecules which have absorbed ultraviolet photons, in order to determine molecular orbital energies in the valence region. If Einstein's photoelectric law is applied to a free molecule, the kinetic energy (formula_1) of an emitted photoelectron is given by where "h" is Planck's constant, ν is the frequency of the ionizing light, and I is an ionization energy for the formation