Which of the following elements can be detected by XPS?
A. Hydrogen and lithium
B. Boron and helium
C. Lithium and boron
The answer is C.
X-ray photoelectron spectroscopy (XPS) is a technique that is used to analyze the elemental composition and chemical state of a material's surface. It works by bombarding the material with X-rays and measuring the energies of the emitted photoelectrons.
To determine which elements can be detected by XPS, we need to consider the characteristics of the X-ray radiation and the ability of different elements to emit photoelectrons.
In terms of X-ray radiation, the energy of the X-rays typically used in XPS ranges from a few hundred electron volts (eV) to a few thousand eV. This energy range allows for the detection of elements up to a certain atomic number because the binding energy of the photoelectrons varies with the atomic number.
Regarding the ability of different elements to emit photoelectrons, elements with low atomic numbers typically have low binding energies, making them easier to detect using XPS. As the atomic number increases, the binding energies increase, and it becomes more challenging to detect those elements using XPS.
Now let's examine the options given:
A. Hydrogen and lithium: Hydrogen has the lowest atomic number (Z = 1), and lithium has a relatively low atomic number (Z = 3). Both hydrogen and lithium have relatively low binding energies, making them detectable by XPS. Therefore, option A is correct.
B. Boron and helium: Boron has an atomic number of 5, which is higher than lithium. As the atomic number increases, the binding energy also increases, making it more challenging to detect elements like boron. Helium, with an atomic number of 2, has even higher binding energy and is less likely to be detected using XPS. Therefore, option B is incorrect.
C. Lithium and boron: We already established that both lithium and boron can be detected by XPS. Therefore, option C is correct.
In summary, the correct answer is options A and C. Both hydrogen, lithium, and boron can be detected by XPS.