Normal-incidence grating spectrograph with large acceptance for inverse photoemission

Abstract

A spectrometer for inverse photoemission in the vacuum ultraviolet range is described. A spherical grating with an acceptance of f/4 is used in normal incidence. Two position-sensitive detectors allow the registration of spectra covering the whole range of photon energies from 8 to 28 eV in parallel. The optical resolution is 18 Å for the Lyman-α line of hydrogen. A space-charge-limited electron gun with an energy spread of 0.25 eV is used to excite inverse photoemission spectra. The large acceptance angle of the grating allows one to measure spectra with high efficiency and low background level.

Principle and application of low energy inverse photoemission spectroscopy: A new method for measuring unoccupied states of organic semiconductors

“…For the analysis of photons in the VUV range, spectrometers have been also used [38][39][40][41][42][43][44][45][46]. However, these spectrometers were low in the photon detection efficiency because of the low reflectivity of gratings in the VUV range and the small solid angel of photon collection.…”

Near-ultraviolet inverse photoemission spectroscopy using ultra-low energy electrons

“…In addition, the asymmetric response function of the detector and its low energy resolution have prevented a precise analysis of the spectral peaks. In this regard, the TPE mode using spectrometers or spectrographs has an advantage in that much higher freedom in the choice of the energy and resolution is available and the response function is well-defined [18][19][20]. The sensitivity, however, is lower by one order of magnitude than the bandpass detectors because of the small acceptance angle of the grating and focusing optics [1].…”

Low-energy inverse photoemission spectroscopy using a high-resolution grating spectrometer in the near ultraviolet range

“…So far, IPES has been performed using grating spectrometers in the vacuum ultraviolet (VUV) range, with photon energies between 10 and 100 eV. [24][25][26][27][28][29][30][31][32] There are several drawbacks. First, the collection efficiency of photons is limited by the solid angle of the grating.…”

“…However, the reflectance of the aluminum coated mirrors is low in the VUV range (particularly below 170 nm) and the surface easily deteriorates in air. 33 In order to design a spectrometer without mirrors, a concave or toroidal grating has been used for IPES at grazing angles, 24 and at the normal angle with the Roland circle [25][26][27][28] or off-Roland circle [29][30][31][32] configurations. The diffraction efficiency of such gratings is in the range of 4% 27,31 to 15%.…”

“…The measurements are made both in the isochromat and TPE modes. The performance is discussed in comparison with the reported IPES apparatus with the grating spectrometers [24][25][26][27][28][29][30][31][32] and the previous LEIPS apparatus using the bandpass filter. 34…”