hi i recently studied about complex coordination in semiconductor. but i dont know what is the meaning of antibonding level. please answer me. thank you.
Dear Sung BIN Lim,
You may want to look at the data presented below:
By Anne Marie Helmenstine, Ph.D.
Updated on November 04, 2019
An antibonding orbital is a molecular orbital containing an electron outside the region between the two nuclei.
As two atoms approach each other, their electron orbitals begin to overlap. This overlap forms a molecular bond between the two atoms with its own molecular orbital shape. These orbitals follow the Pauli exclusion principle in the same way as atomic orbitals. No two electrons in an orbital can have the same quantum state. If the original atoms contain electrons where a bond would violate the rules, the electron will populate the higher energy antibonding orbital.
Antibonding orbitals are denoted by an asterisk symbol next to the associated type of molecular orbital. σ* is the antibonding orbital associated with sigma orbitals and π* orbitals are antibonding pi orbitals. When speaking of these orbitals, the word 'star' is often added to the end of the orbital name: σ* = sigma-star.
Examples
H2- is a diatomic molecule containing three electrons. One of the electrons is found in an antibonding orbital.
Hydrogen atoms have a single 1s electron. The 1s orbital has room for 2 electrons, a spin "up" electron and a spin "down" electron. If a hydrogen atom contains an extra electron, forming an H- ion, the 1s orbital is filled.
If an H atom and H- ion approach each other, a sigma bond will form between the two atoms. Each atom will contribute an electron to the bond filling the lower energy σ bond. The extra electron will fill a higher energy state to avoid interacting with the other two electrons. This higher energy orbital is called the antibonding orbital. In this case, the orbital is a σ* antibonding orbital.
Sources
- Atkins P.; de Paula J. (2006). Atkins Physical Chemistry (8th ed.). W.H. Freeman. ISBN:0-7167-8759-8.
- Orchin, M.; Jaffe, H.H. (1967). The Importance of Antibonding Orbitals. Houghton Mifflin. ISBN:B0006BPT5O.
https://www.thoughtco.com/definition-of-antibonding-orbital-604784
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Abstract and figures
The spin-orbit interaction is a crucial element of many semiconductor spintronic technologies. Here we report the first experimental observation, by magneto-optical spectroscopy, of a remarkable consequence of the spin-orbit interaction for holes confined in the molecular states of coupled quantum dots. As the thickness of the barrier separating two coupled quantum dots is increased, the molecular ground state changes character from a bonding orbital to an antibonding orbital. This result is counterintuitive, and antibonding molecular ground states are never observed in natural diatomic molecules. We explain the origin of the reversal using a four band k.p model that has been validated by numerical calculations that account for strain. The discovery of antibonding molecular ground states provides new opportunities for the design of artificially structured materials with complex molecular properties that cannot be achieved in natural systems.
https://www.researchgate.net/publication/1920088_Antibonding_ground_states_in_semiconductor_artificial_molecules
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Picture the allowed states of a bound electron. The lowest energy state, like the fundamental vibration of a plucked string has an antinode in the middle. If you ask, “Where is the electron?”, you would say the electron is mostly in the middle. Now the next higher energy state, like the first harmonic of a plucked string, has a node in the middle and two antinodes to either side. You would say the electron is mostly not in the middle. The states in the vicinity of two atomic nuclei are more complicated, but basically they have this same property. As you go up in energy every other state has a node in the middle, and that means the electron is mostly not in the middle. The location of the electric charge determines the bonding. The two positively charged atomic nuclei are repulsive and would fly apart. The negative charge of the electron being mostly between the nuclei screens them from each other and holds them bound. States that have a node in the middle are less effective at screening the nuclei and so less effective at holding them together. So odd energy states that have an antinode in the middle are called “bonding” because they are more effective at screening the nuclei and holding them together, and even energy states which have a node in the middle are called “antibonding” because they don’t effectively screen the nuclei and they repulse.
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