predissociationn.
/ˌpriːdᵻˌsəʊʃɪˈeɪʃən/, /ˌpriːdᵻˌsəʊsɪˈeɪʃn/, U.S. /ˈpridᵻˌsoʊʃiˈeɪʃ(ə)n/, /ˈpridᵻˌsoʊsiˈeɪʃ(ə)n/ Physics and Chemistry.
The passage of a molecule between a quantized vibrational and rotational state (above its ground state) and an unquantized dissociated state of the same energy, resulting in certain bands in the spectrum of the molecule being diffuse instead of having the normal rotational fine structure.
ΘΚΠ
the world > matter > physics > atomic physics > decomposition of light, spectrum > [noun] > passage between states
predissociation1924
1924 V. Henri & M. C. Teves in Nature 20 Dec. 895/1 The molecule can be modified in its internal structure: the atoms are driven apart, the bonds are weakened, the molecule becomes more reactive, and the rotational movements are no longer quantified. This first modification is a preliminary preparation of the molecule for its total dissociation, and it is necessary to introduce a new term for this change. We propose to denote it by the term predissociation of the molecule.
1944 S. Glasstone Theoret. Chem. iv. 188 In some cases the predissociation spectrum is followed by a region of continuous absorption.
1962 P. J. Durrant & B. Durrant Introd. Adv. Inorg. Chem. vii. 222 Predissociation is commonly shown only in absorption, not in emission.
2001 Proc. National Acad. Sci. U.S.A. 98 2976/2 Another option..is the predissociation of the neutral excited state that is used as an intermediate in reaching the Rydberg state.
This entry has been updated (OED Third Edition, March 2007; most recently modified version published online March 2022).
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n.1924