<p>In near-ambient pressure photoelectron spectroscopy, photoelectron intensity is greatly reduced due to scattering of photoelectrons in gas. Therefore, in general, the distance d between the sample and the aperture cone is set as small as possible within a range in which the pressure drop on the sample surface does not occur. Recently, however, we have reported that increasing d has a significant effect on the environmental charge compensation in the measurement of insulators [1-4]. There have been few reports on the detailed relationship between photoelectron intensity and d in near-ambient pressure photoemission spectroscopy. In this study, we investigated the d dependence of photoelectron intensity in near-ambient pressure photoemission spectroscopy by varying d over a wide range [5].</p><p></p><p>Experiments were carried out using a near-ambient pressure hard X-ray photoelectron spectroscopy apparatus installed at Hyogo Prefecture ID beamline BL24XU in SPring-8. The excitation X-ray energy was 8 keV. In our usual arrangement, d = 0.3 mm. Here, however, we varied d greatly in the range of 0.3 to 5 mm and investigated the gas (Ar or N₂) pressure P dependence of the photoelectron intensity from the Au plate at each d. Ta. See reference [1] for details on how to change d.</p><p></p><p>ln (I / Io) decreased linearly with P at each d, as expected from the Beer-Lambert law, I / Io = exp (- σ P d / k_B T). where I and Io are photoelectron intensities in gas and vacuum, and σ is the electron scattering cross section. From these measurements, it was found that increasing d in charging-free measurements of an insulator is also advantageous from the viewpoint of photoelectron intensity. From the slope of the ln (I / Io) vs P plot, the value of σ d was obtained for each d. Figure 1 shows the relationship between σ d and d obtained. Clearly the straight line obtained here does not pass through the origin. To reproduce this result, it is necessary to change d to d + do (do is a constant of about 1 mm) in the Beer-Lambert law. It is considered that the correction is necessary due to the effect of residual gas in the electron lens.</p><p></p><p>References:</p><p>[1] S. Suzuki et al., J. Electron. Spectrosc. Relat. Phenom. 257, 147192 (2022).</p><p>[2] K. Fujitani et al., Heliyon 9, e15794 (2023).</p><p>[3] K. Fujitani et al., Appl. Surf. Sci. 637, 157891 (2023).</p><p>[4] K. Takahara et al., Adv. X-ray Chem. Anal., Jpn 54, 75 (2023).</p><p>[5] S. Suzuki et al., J. Vac. Sci. Technol. B 41, 044204 (2023).</p>