metastableadj.
/ˌmɛtəˈsteɪbl/, U.S. /ˈˌmɛdəˈˌsteɪb(ə)l/ 1. Science. Designating, relating to, or existing in a state of apparent stability that is capable of changing to a more stable state when subjected to perturbation. Also (of a metal, glass, liquid, etc.): continuing in a state with more energy than the most stable state, to which it is unable to pass.
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the world > matter > chemistry > physical chemistry > [adjective] > systems
metastable1897
the world > matter > chemistry > chemical reactions or processes > [adjective] > of or relating to named chemical reactions or processes > of or relating to metastability
metastable1941
1897 Jrnl. Chem. Soc. 72 ii. 309 The author gives to the above form of instability, where the change to solid can only be caused by the presence of the solid itself, the name of ‘metastabile’ [sic].
1897 Jrnl. Chem. Soc. 72 ii. Index 777/1 Equilibrium, metastable and labile.
1899 J. Walker Introd. Physical Chem. xi. 101 A supercooled liquid may be kept for a very long time without any solid appearing, but as soon as the smallest particle of the substance in the more stable solid phase is introduced, the less stable, or, as it has been called, the metastable phase is transformed into it.
1913 Engineering 10 Oct. 510/3 The under-cooled liquid phase can in many cases be retained in the metastable condition at temperatures far below the normal freezing-point by a process of under~cooling.
1941 J. H. Keenan Thermodynamics xxiii. 404 A marble at rest at the bottom of the higher of two depressions in a continuous surface is an example of metastable equilibrium.
1968 C. G. Kuper Introd. Theory Superconductivity i. 11 Long-lived metastable states cannot be rejected a priori as impossible. Diamond at room temperature shows no tendency to graphitize, nor glass to crystallize. But in all cases like these the excess entropy is frozen in by the immobility of the atoms at low temperatures.
1981 Metall. Trans. 12 A. 695 Metastable structures or, more accurately, configurationally frozen metastable structures are no novelty in metallurgy.
1997 Nature 6 Mar. 23/1 These crystals are in a metastable condition; they want to transform to a well defined low-symmetry structure on cooling, but are structurally ‘frustrated’ from doing so.
2. Physics. Of an excited state of an atom, nucleus, particle, etc.: having an exceptionally long lifetime because the transitions to states of lower energy are forbidden transitions.
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the world > matter > physics > quantum theory > raising energy level, excitation > [adjective] > having long lifetime
metastable1921
1921 Chem. Abstr. 15 3931 Recent researches..lead to the establishment of the existence of excited atoms in a metastable state.
1922 A. D. Udden tr. N. Bohr Theory of Spectra iii. 86 These experiments showed that the impact of electrons could bring helium into a ‘metastable’ state from which the atom cannot return to its normal state by means of a simple transition.
1942 J. D. Stranathan ‘Particles’ of Mod. Physics xi. 455 It seems that certain nuclei can exist for considerable time in an excited state, known as a metastable state.
1961 J. L. Powell & B. Crasemann Quantum Mech. xii. 458 The ground state of the orthohelium system..is therefore stable with respect to optical transitions of the usual kind, and has a correspondingly long lifetime. For this reason, it is frequently referred to as a metastable state.
1973 Sci. Amer. Feb. 93/2 The singlet and triplet metastable states have long lifetimes because they have no means of radiating their energy.
1994 Nature 28 Apr. 813/2 Last year saw the production at CERN of gas-phase, metastable antiprotonic helium atoms (a helium atom with an antiproton substituted for one of the electrons).
This entry has been updated (OED Third Edition, December 2001; most recently modified version published online March 2022).
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adj.1897