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  2. Spontaneous process - Wikipedia

    en.wikipedia.org/wiki/Spontaneous_process

    When ΔS > 0 and ΔH < 0, the process is always spontaneous as written. When ΔS < 0 and ΔH > 0, the process is never spontaneous, but the reverse process is always spontaneous. When ΔS > 0 and ΔH > 0, the process will be spontaneous at high temperatures and non-spontaneous at low temperatures. When ΔS < 0 and ΔH < 0, the process will be ...

  3. Thermodynamic free energy - Wikipedia

    en.wikipedia.org/wiki/Thermodynamic_free_energy

    For a process at constant temperature and pressure without non-PV work, this inequality transforms into <. Similarly, for a process at constant temperature and volume, <. Thus, a negative value of the change in free energy is a necessary condition for a process to be spontaneous; this is the most useful form of the second law of thermodynamics ...

  4. Second law of thermodynamics - Wikipedia

    en.wikipedia.org/wiki/Second_law_of_thermodynamics

    or dG < 0. For a similar process at constant temperature and volume, the change in Helmholtz free energy must be negative, <. Thus, a negative value of the change in free energy (G or A) is a necessary condition for a process to be spontaneous. This is the most useful form of the second law of thermodynamics in chemistry, where free-energy ...

  5. Helmholtz free energy - Wikipedia

    en.wikipedia.org/wiki/Helmholtz_free_energy

    and thus for a system kept at constant temperature and volume and not capable of performing electrical or other non-PV work, the total free energy during a spontaneous change can only decrease. This result seems to contradict the equation dF = −S dT − P dV, as keeping T and V constant seems to imply dF = 0, and hence F = constant.

  6. Spontaneous symmetry breaking - Wikipedia

    en.wikipedia.org/wiki/Spontaneous_symmetry_breaking

    Spontaneous symmetry breaking is a spontaneous process of symmetry breaking, by which a physical system in a symmetric state spontaneously ends up in an asymmetric state. [ 1 ] [ 2 ] [ 3 ] In particular, it can describe systems where the equations of motion or the Lagrangian obey symmetries, but the lowest-energy vacuum solutions do not exhibit ...

  7. Non-equilibrium thermodynamics - Wikipedia

    en.wikipedia.org/wiki/Non-equilibrium_thermodynamics

    The suitable relationship that defines non-equilibrium thermodynamic state variables is as follows. When the system is in local equilibrium, non-equilibrium state variables are such that they can be measured locally with sufficient accuracy by the same techniques as are used to measure thermodynamic state variables, or by corresponding time and space derivatives, including fluxes of matter and ...

  8. File:Scheme of spontaneous parametric down-conversion.pdf

    en.wikipedia.org/wiki/File:Scheme_of_spontaneous...

    You are free: to share – to copy, distribute and transmit the work; to remix – to adapt the work; Under the following conditions: attribution – You must give appropriate credit, provide a link to the license, and indicate if changes were made.

  9. Stimulated Raman spectroscopy - Wikipedia

    en.wikipedia.org/wiki/Stimulated_Raman_spectroscopy

    Stimulated Raman spectroscopy, also referred to as stimulated Raman scattering (SRS), is a form of spectroscopy employed in physics, chemistry, biology, and other fields. . The basic mechanism resembles that of spontaneous Raman spectroscopy: a pump photon, of the angular frequency , which is scattered by a molecule has some small probability of inducing some vibrational (or rotational ...