quantum mechanics

(noun)

The branch of physics that studies matter and energy at the level of atoms and other elementary particles; it substitutes probabilistic mechanisms for classical Newtonian ones.

Related Terms

Examples of quantum mechanics in the following topics:

  • Implications of Quantum Mechanics

    • The field of quantum mechanics has been enormously successful in explaining many of the features of our world.
    • Quantum mechanics has also strongly influenced string theory.
    • The application of quantum mechanics to chemistry is known as quantum chemistry.
    • Relativistic quantum mechanics can, in principle, mathematically describe most of chemistry.
    • Explain importance of quantum mechanics for technology and other branches of science

  • Philosophical Implications

    • Since its inception, many counter-intuitive aspects of quantum mechanics have provoked strong philosophical debates.
    • This is due to the quantum mechanical principle of wave function collapse.
    • One of the most bizarre aspect of the quantum mechanics is known as quantum entanglement.
    • According to the Copenhagen interpretation of quantum mechanics, their shared state is indefinite until measured.
    • Formulate the Copenhagen interpretation of the probabilistic nature of quantum mechanics

  • A Physical Aside: Einstein coefficients

    • Fermi's Golden Rule relates the cross-section for a process to a quantum mechanical matrix element and the phase space available for the products.
    • Because quantum mechanics for the most part is time reversible, the cross-section for the forward and reverse reactions are related.

  • The Wave Function

    • A wave function is a probability amplitude in quantum mechanics that describes the quantum state of a particle and how it behaves.
    • In quantum mechanics, a wave function is a probability amplitude describing the quantum state of a particle and how it behaves.
    • The laws of quantum mechanics (the Schrödinger equation) describe how the wave function evolves over time.
    • This figure shows some trajectories of a harmonic oscillator (a ball attached to a spring) in classical mechanics (A-B) and quantum mechanics (C-H).
    • In quantum mechanics (C-H), the ball has a wave function, which is shown with its real part in blue and its imaginary part in red.

  • Quantum-Mechanical View of Atoms

    • Hydrogen-1 (one proton + one electron) is the simplest form of atoms, and not surprisingly, our quantum mechanical understanding of atoms evolved with the understanding of this species.
    • Modern quantum mechanical view of hydrogen has evolved further after Schrödinger, by taking relativistic correction terms into account.
    • Quantum electrodynamics (QED), a relativistic quantum field theory describing the interaction of electrically charged particles, has successfully predicted minuscule corrections in energy levels.
    • One of the hydrogen's atomic transitions (n=2 to n=1, n: principal quantum number) has been measured to an extraordinary precision of 1 part in a hundred trillion.
    • This kind of spectroscopic precision allows physicists to refine quantum theories of atoms, by accounting for minuscule discrepancies between experimental results and theories.

  • de Broglie and the Wave Nature of Matter

    • In quantum mechanics, the concept of matter waves (or de Broglie waves) reflects the wave-particle duality of matter.
    • This was a pivotal result in the development of quantum mechanics.
    • Further, recent experiments confirm the relations for molecules and even macromolecules, normally considered too large to undergo quantum mechanical effects.

  • Lasers

    • Principles of laser operation are largely based on quantum mechanics.
    • This is the mechanism of fluorescence and thermal emission.
    • However, an external photon at a frequency associated with the atomic transition can affect the quantum mechanical state of the atom .

  • Atomic Structure

    • We also derived some important relationships between how atoms emit and absorb radiation, but to understand atomic processes in detail we will have to treat the electrons quantum mechanically.
    • In quantum mechanics we characterize the state of a particles (or group of particles) by the wavefunction ($\Psi$).

  • The Bohr Model of the Atom

    • Bohr suggested that electrons in hydrogen could have certain classical motions only when restricted by a quantum rule.
    • Bohr's theory explained the atomic spectrum of hydrogen, made him instantly famous, and established new and broadly applicable principles in quantum mechanics.
    • The laws of classical mechanics predict that the electron should release electromagnetic radiation while orbiting a nucleus (according to Maxwell's equations, accelerating charge should emit electromagnetic radiation).
    • The significance of the Bohr model is that the laws of classical mechanics apply to the motion of the electron about the nucleus only when restricted by a quantum rule.
    • His many contributions to the development of atomic physics and quantum mechanics; his personal influence on many students and colleagues; and his personal integrity, especially in the face of Nazi oppression, earned him a prominent place in history.

  • Planck's Quantum Hypothesis and Black Body Radiation

    • Planck's quantum hypothesis is a pioneering work, heralding advent of a new era of modern physics and quantum theory.
    • Although Planck's derivation is beyond the scope of this section (it will be covered in Quantum Mechanics), Planck's law may be written:
    • Planck's quantum hypothesis is one of the breakthroughs in the modern physics.