Experimental transmittance and reflectance spectroscopy system. The incidence angle is 8°. P1, P2, and P3 stand for the silicon photodiodes. Photodiode P3 monitors the incident intensity to normalize the reflected and transmitted signals measured by P1 and P2 in case of lamp intensity variations. The chopper frequency is around . The wavelength range is limited by the tungsten halogen lamp spectrum and second order diffraction in the monochromator.
Reflectance and transmittance measurements for sample Pd-1 after exposure to of hydrogen.
Graphs (a) and (c) resume measurements for the three Pd samples for the first cycle of hydrogen exposure and (b) and (d) for the second cycle.
Behavior of the real part and the imaginary part of the refractive index of sample Pd-1 for different pressures during second cycle. The vertical dashed lines indicate the times at which the different hydrogen pressures are admitted into the vacuum chamber. From left to right: 3.5, 17.5, 26, 35, 44, , and vacuum.
Complex refractive index of sample Pd-1 as a function of wavelength at saturation for the pressures of 3.5, 17.5, 26, 35, 44, and . The arrows show the direction of increasing pressure.
Real and imaginary parts of refractive index of samples Pd-1 (square), Pd-2 (triangle), and Pd-3 (circle) for second hydrogen exposure cycle. The extinction coefficient corresponds to the solid lines and the real part to the dashed lines.
(a) Reflectance in dashed lines and transmittance in continuous lines of PdO film exposed to of hydrogen. The oxide reduces to metallic palladium. The transmittance tends to be plain and anomalously high owed to destruction of the film in final stages of reduction. Graph (b) shows the components of the refractive index of the same sample of the first nine scans. The arrows show the direction in which the curves evolve with increasing time. The time difference among scans is .
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