Rhenium

Doublet Separations

Re 4f: 2.4 eV
Re 4d: 13.4 eV
Re 4p: 71.9 eV

Available Photoemissions and Energies

The Energies Listed are Binding Energies!

Re 4s: 625 eV
Re 4p: 445 eV
Re 4d: 260 eV
Re 4f: 40 eV

Common Element Overlaps

The Energies Listed are Binding Energies!

Re is primarily analysed via the 4f orbital

V 3p (38 eV)
Sr 4s (38 eV)
Te 4d (40 eV)
Ne 2s (41 eV)
As 3d (41 eV)
Tm MNN a (Al source) (43 eV)
Cr 3p (43 eV)
Ru 4p (43 eV)
Ca 3s (44 eV)
Y 4s (46 eV)

Augers and Energies

Energies listed are Kinetic Energies!

Re NOO: ~ 160 eV

Common Species Binding Energies

The Energies Listed are Binding Energies!

Material	Re(4f ⁷/₂) Binding Energy / eV	Reference
Re Metal	40.4 (Calibrated to Fermi Level)	[2]
Re₂O₇	46.8 (Calibrated to C(1s) at 284.8 eV)	[1, 2]
NH₄ReO₄	46.3 (Calibrated to C(1s) at 284.8 eV)	[2]
ReO₂	43.0 (Std. Dev. of 0.6 eV)	[2] , ([3])
ReO₃	44.2 (Std. Dev of 1.3 ev)	[2] , ([3])

Table 1. Binding energies of common Re states

Typically considered to be one of the most stable elements due to its high melting and boiling points, rhenium is often found in nickel based superalloys, but also finds use in olefin metathesis and reforming catalysis. Rhenium can exhibit multiple oxidation states, with +7, +6, +4 and +2 the most common in materials analysed by XPS.

Figure 1, shows the spectra of a partially oxidised rhenium foil exhibiting metallic Re (green), ReO₂ (blue) and Re₂O₇ (yellow) states.

Figure 1. Rhenium foil with Re, ReO2 and Re2O7 species present. Note for fitting the Shirley background has been offset suggesting a different background may be more suitable here.

Experimental Advice

High valence rhenium oxides can undergo disproportionation during XPS analysis [1], so a suitable methodology, such as rapid acquisition and recording the Re(4f) region first and again at the end should be considered.

Fitting Advice

Sb metal exhibits a modicum of asymmetry, for example – the clean Sb metal surface below may be fit with an LF(0.65,0.69,60,100,10) lineshape with the appropriate background. Important to note also, is the shake-up structure appearing at ~544 eV. The data below is available online via work from HarwellXPS technical director Dr. David Morgan at Surface Science Spectra.

Fitting of the overlapping (with O 1s) Sb 3d 5/2 peak is made easier through using the unaffected 3d 3/2 peak. Peak constraints may be used to fix the overlapping peak to the ‘free’ peak, particularly important in the case of multiple Sb states.