X-ray impact induced desorption of gases from surfaces

Abstract

Measurements of gases released from 302 stainless steel and gold surfaces before and after discharge cleaning were made in ultrahigh vacuum using X-rays with an energy distribution typical of a tungsten bremsstrahlung spectrum. Similar measurements were also made for Al 2O 3 surfaces which had not been discharge cleaned. For the non-discharge-cleaned surfaces of stainless steel, Al 2O 3, and gold the predominant gas species observed mass spectrometrically was CO 2. For some stainless steel and Al 2O 3 surfaces CO and O 2 were also readily observed. Mean quantum yields for CO, O 2 and CO 2 release from such stainless steel surfaces, for example, ranged from < 6 × 10 −5 to 9 × 10 −4 molecules per photons in the bremsstrahlung spectrum characteristic for 50 keV electron energy. After discharge cleaning a decrease in the mean quantum yields was observed for the stainless steel and gold surfaces.