Question

In 1996 , physicists created an anti-atom of hydrogen. In such an atom, which is the antimatter equivalent of an ordinary atom, the electric charges of all the component particles are reversed. Thus the nucleus of an anti-atom is made of an antiproton, which has the same mass as a proton but bears a negative charge, while the electron is replaced by an anti-electron (also called a positron) with the same mass as an electron, but bearing a positive charge. Would you expect the energy levels, emission spectra, and atomic orbitals of an antihydrogen atom to be different from those of a hydrogen atom? What would happen if an anti-atom of hydrogen collided with a hydrogen atom?

Short answer

The energy levels and spectra of antihydrogen match hydrogen. Collision with hydrogen results in annihilation and energy release.

Step-by-step solution

Understanding the Context of Anti-atom

In an anti-atom, the electric charges of the particles are reversed compared to an ordinary atom. The nucleus of an antihydrogen atom is an antiproton, which bears a negative charge instead of the positive charge of a proton. Similarly, the anti-electron or positron in antihydrogen is positively charged as opposed to the negatively charged electron in hydrogen.

Analyzing Energy Levels and Orbitals

The energy levels, emission spectra, and atomic orbitals of an atom are determined by the masses and charges of its subatomic particles and the electromagnetic forces between them. In an antihydrogen atom, the mass and nature of the interactions are identical to those in ordinary hydrogen, except that the charges are reversed. As a result, these aspects should be the same for both hydrogen and antihydrogen, since the physics governing the interactions is symmetric with respect to charge inversion.

Assessing Collision between Hydrogen and Antihydrogen

When an anti-atom of hydrogen collides with a hydrogen atom, matter and antimatter are present. Such a collision would typically result in annihilation, where the antiproton and proton destroy each other, and the electron and positron pair do as well. This process releases energy in the form of high-energy photons or gamma rays, due to the complete conversion of matter and antimatter into energy.

Key concepts

Antimatter

Antimatter is the opposite of regular matter in terms of its electric charge. For every particle of ordinary matter, such as electrons and protons, there is an equivalent antiparticle. When it comes to antihydrogen, it consists of an antiproton and a positron.
- **Antiproton:** This is negatively charged, unlike a regular proton which is positively charged.
- **Positron:** This is the antimatter counterpart of an electron and carries a positive charge.
The existence of antimatter was first theorized by physicists as a result of equations in quantum mechanics. When matter and antimatter meet, they annihilate each other, releasing energy. This means that when an antihydrogen atom comes into contact with a hydrogen atom, they will annihilate, producing energy, generally in the form of gamma-ray photons.

Energy Levels

Energy levels in atoms are the specific energies that electrons or antiparticles can have while orbiting the nucleus. In both matter and antimatter, these levels are determined by the interactions of the particles’ charges and masses with electromagnetic forces.
- For antihydrogen, the energy levels are expected to be identical to hydrogen because the only difference is the reversal of charge, not mass or the nature of interactions.
This is due to the charge symmetry in physical laws, meaning that changing charge does not alter the basic properties governing energy levels. Consequently, antihydrogen should exhibit similar stability in its energy levels as regular hydrogen.

Emission Spectra

Emission spectra are the distinct lines of color or light, unique to each element, emitted when electrons transition between energy levels. Antihydrogen is anticipated to have the same emission spectra as hydrogen.
- The reason lies in the symmetric nature of electromagnetic interactions. Since the mass of electrons and positrons is identical and the charge reversal affects nothing but the direction of attraction or repulsion, the transition energies remain unchanged.
Thus, the light emitted during positron transitions in antihydrogen would match that of electron transitions in hydrogen, making their emission spectra practically indistinguishable.

Atomic Orbitals

Atomic orbitals describe the region in space where there is a high probability of finding an electron in an atom or antimatter counterpart in an anti-atom. For hydrogen and antihydrogen, these orbitals are similarly shaped and arranged.
- The concept of orbitals arises from the quantum mechanical model, which is equally applicable to both matter and antimatter since it relies on wave functions not affected by charge reversal.
This means that the spatial distribution of the positron in antihydrogen will mirror that of the electron in hydrogen, maintaining the consistency of atomic orbitals. Therefore, any experiments conducted would show that, in terms of orbital structure, antihydrogen and hydrogen are twins.