Which of the following are excited in ultraviolet photoelectron spectroscopy?
A. Valence electrons
B. Core electrons
C. X-rays
What's the answer
In ultraviolet photoelectron spectroscopy (UPS), valence electrons are the ones excited and detected. Therefore, option A, valence electrons, is the correct choice.
To arrive at this answer, you can use your knowledge of the technique. UPS involves shining ultraviolet light onto a sample and measuring the energy of electrons that are ejected from it. The energy of these ejected electrons corresponds to the energy levels of valence electrons, which are the outermost electrons involved in chemical bonding.
On the other hand, core electrons (option B) are electrons that occupy the inner energy levels of an atom or molecule. These electrons are more tightly bound and require more energy, usually in the form of X-rays, to be excited. Therefore, option C, X-rays, are used to excite core electrons, not in ultraviolet photoelectron spectroscopy.
So, the correct answer is A. Valence electrons.