physical chemistry Physical chemistry is the study of macroscopic and microscopic phenomena in chemical systems in terms of the principles, practices, and concepts of physics such as motion, energy, force, time, thermodynamics, quantum chemistry, statistica ...

, a hot atom is an

atom Every atom is composed of a nucleus and one or more electrons bound to the nucleus. The nucleus is made of one or more protons and a number of neutrons. Only the most common variety of hydrogen has no neutrons. Every solid, liquid, gas, ...

that has a high kinetic or internal energy. When

molecule A molecule is a group of two or more atoms held together by attractive forces known as chemical bonds; depending on context, the term may or may not include ions which satisfy this criterion. In quantum physics, organic chemistry, and bioche ...

AB adsorbs on a surface dissociatively, # both A and B adsorb on the surface, or # only A adsorbs on the surface, and B desorbs from the surface. In case 2, B gains a high translational energy from the adsorption energy of A, and hot atom B is generated. For example, the

hydrogen Hydrogen is the chemical element with the symbol H and atomic number 1. Hydrogen is the lightest element. At standard conditions hydrogen is a gas of diatomic molecules having the formula . It is colorless, odorless, tasteless, non-toxic ...

, because of its light mass, gets a high translational energy. Such a hot atom does not fly into vacuum but is trapped on the surface, where it diffuses with high energy. Hot atoms are expected to play important roles in catalytic reactions. For example, a reaction of a

atom with hydrogen atoms on a

silicon Silicon is a chemical element with the symbol Si and atomic number 14. It is a hard, brittle crystalline solid with a blue-grey metallic luster, and is a tetravalent metalloid and semiconductor. It is a member of group 14 in the periodic ta ...

surface and a reaction of an

oxygen Oxygen is the chemical element with the symbol O and atomic number 8. It is a member of the chalcogen group in the periodic table, a highly reactive nonmetal, and an oxidizing agent that readily forms oxides with most elements as ...

atom with oxygen molecules on Pt(111) have been reported. Hot atoms can also be generated by degenerating molecules on a metal surface with UV light. It has been reported that the reactivity of an

generated in such a way on a

platinum Platinum is a chemical element with the symbol Pt and atomic number 78. It is a dense, malleable, ductile, highly unreactive, precious, silverish-white transition metal. Its name originates from Spanish , a diminutive of "silver". Pla ...

surface is different from that of chemisorbed

atoms. Elucidating the role of hot atoms on surfaces will lead to a deeper understanding of the mechanism of reactions.

References

See also