![]() The inner core electronic configuration of the initial state of the Pd is: This arises from spin-orbit coupling effects in the final state. The 3 d photoemission is in fact split between two peaks, one at 334.9 eV BE and the other at 340.2 eV BE, with an intensity ratio of 3:2. We can see this more clearly if, for example, we expand the spectrum in the region of the 3 d emission. the peak intensities are not simply related to the electron occupancy of the orbitalsĬloser inspection of the spectrum shows that emission from some levels (most obviously 3 p and 3 d ) does not give rise to a single photoemission peak, but a closely spaced doublet.there are significant differences in the natural widths of the various photoemission peaks.330 eV (in this case it is really meaningless to refer to an associated binding energy). the remaining peak is not an XPS peak at all ! - it is an Auger peak arising from x-ray induced Auger emission.335 eV is due to emission from the 3 d levels of the Pd atoms, whilst the 3 p and 3 s levels give rise to the peaks at ca. the emission from the 4 p and 4 s levels gives rise to very weak peaks at 54 eV and 88 eV respectively.4 - 12 eV if measured with respect to the vacuum level ). 0 - 8 eV ( measured with respect to the Fermi level, or alternatively at ca. the valence band (4 d, 5 s) emission occurs at a binding energy of ca.Working downwards from the highest energy levels. The most intense peak is now seen to occur at a binding energy of ca. Since the photon energy of the radiation is always known it is a trivial matter to transform the spectrum so that it is plotted against BE as opposed to KE. the main peaks occur at kinetic energies of ca. The diagram below shows a real XPS spectrum obtained from a Pd metal sample using Mg K α radiation Until now there has been no significant detection of potassium in high resolution observations for any exoplanet.\): The XPS spectrum of Pd metal "During transit, we then detected the potassium signature, which disappeared before and after transit as expected, which indicates that the absorption is induced by the planetary atmosphere." Investigations by other teams already attempted to detect potassium on the same exoplanet, however, either nothing was found or what was found was too weak to be statistically significant. student at AIP in the group Stellar Physics and Exoplanets. "We took a time series of light spectra during the transit and compared the absorption depth," says the lead author of the study, Engin Keles, Ph.D. It requires that the exoplanet transits in front of the host star. The technique that was applied for this study at LBT is called transmission spectroscopy. The blue line shows the modelled planetary absorption. Vertical dashed lines indicate the transit duration. The horizontal axis shows the time in minutes, 0 means the exoplanet is at the central meridian near the middle of the stellar disk. The animation depicts the excess absorption in the potassium line in the expoplanet’s atmosphere during transit compared to the light absorption from the exoplanet itself. With these new measurements, researchers can now compare the absorption signals of potassium and sodium and thus learn more about processes such as condensation or photo- ionization in these exoplanet atmospheres. It needed the light gathering capability of the 2x8,4m LBT and the high spectral resolution of PEPSI to definitely measure potassium for the first time at high resolution in atmospheric layers above the clouds. The exoplanet, 64 light years away and about the size of Jupiter, orbits its home star-a red giant-in 53 hours and is 30 times closer to it than the Earth to the Sun. Even for HD189733b, the best studied hot Jupiter, so far scientists only possessed a very vague and imprecise knowledge of the potassium absorption. However, the presence of clouds in hot Jupiter atmospheres strongly weakens any spectral absorption features and thus makes them very hard to detect. Different elements cause specific absorption signals in the spectrum, dark lines, that hint at the chemical composition of the atmosphere. The elements can be discovered by analyzing the home star's spectrum of light when the planet passes in front of it as seen from Earth. While sodium was detected with high resolution observations already early on, potassium was not, which created a puzzle for atmospheric chemistry and physics. Ever since the earliest theoretical predictions 20 years ago, the chemical elements potassium and sodium were expected to be detectable in atmospheres of "hot Jupiters," gaseous planets with temperatures of a few thousand Kelvin that orbit closely around far-away stars.
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