| 释义 |
isotopic, a.|aɪsəˈtɒpɪk|
[f. prec. + -ic.]
a. Of, pertaining to, or being an isotope or isotopes of an element; isotopic number, the number of neutrons in a nucleus minus the number of protons.
Before Soddy coined the word in 1913, isotopic had previously (unknown to him) been used in a different sense (see quot. 1904), but this use did not gain currency.
[1904Cohen & Miller in Jrnl. Chem. Soc. LXXXV. 1624 Supposing the bromine in the ortho- and meta-positions to retard oxidation more than the chlorine in these positions, the effect should become apparent when the isotopic dichloro-, chlorobromo-, and dibromo-toluenes are oxidised together. [Note] We propose..to employ the word ‘isotopic’..in place of the rather awkward expression ‘similarly substituted’. ]1913[see isotope 1]. 1919F. Soddy in Jrnl. Chem. Soc. CXV. 18 The chemistry of actinium has been enormously simplified by the discovery that mesothorium-2 is isotopic with it, for the latter may be used as an indicator to show in what way the actinium distributes itself after any chemical treatment. 1920Glasgow Herald 7 Oct. 8 It had now been found that certain elements which hitherto had been stated to have atomic weights fractional were mixtures of isotopes, and such isotopic elements had atomic weights as whole numbers on the oxygen scale. 1921W. D. Harkins in Nature 14 Apr. 202/2 Let us specify the atoms of this important class as those of isotopic number 0. Then the isotopes of magnesium of atomic weights 24, 25, and 26 will have isotopic numbers 0, 1, and 2. Ibid., The isotopic number n is the number which, when added to twice the atomic number, gives the atomic weight. 1933F. W. Aston Mass-Spectra & Isotopes xiv. 176 Atoms of isotopic number 0, such as C12, O16, Mg24, etc., predominate in a marked degree. Abundance is much less for isotopic number 1 such as F19, Na23, Al27, decreases again for 2:—N14, Ne22, and becomes practically zero for 3:—Cl37. 1942J. D. Stranathan ‘Particles’ of Mod. Physics v. 200 Considerable isotopic data has been obtained from studies of hyperfine structure. 1954Sci. News XXXIV. 51 The next simplest use of the mass spectrometer is to measure the quantity of one isotope of an element compared with another—the isotopic ratio as it is called. 1956A. H. Compton Atomic Quest i. 52 The isotopic separation of U-235 from U-238. 1957G. E. Hutchinson Treat. Limnol. I. viii. 549 A study of the isotopic constitution of the sulfur in the sulfate of rain. 1971J. Z. Young Introd. Study Man v. 82 Many of the elements exist in isotopic forms, which break down spontaneously.
b. Of, pertaining to, or designating isospin; orig. and chiefly in isotopic spin = isospin.
1937E. Wigner in Physical Rev. LI. 106/2 W. Heisenberg..considered protons and neutrons as different states of the same particle. Heisenberg introduced a variable τ which we shall call the isotopic spin, the value -1 of this variable can be assigned to the proton state of the particle, the value +1 to the neutron state. Ibid. 107/1 The Pauli principle requires that the wave function Ψ(r1s1τ1, r2s2τ2,{ddd}, rnsnτn) be antisymmetric with respect to the simultaneous interchange of Cartesian, spin and isotopic spin variables of any pair of heavy particles. This fact is quite analogous to the similar statement for ordinary spin. Ibid. 117/1 Terms with different ζ components of the isotopic spin have the same energy in approximation 2. These are, of course, terms of different isobaric nuclei, and a total isotopic spin T will be a term with the same binding energy for all nuclei with isotopic numbers from - T to T. 1953M. Gell-Mann in Physical Rev. XCII. 833/2 Let us suppose that the new unstable particles are fermions with integral isotopic spin and bosons with half⁓integral isotopic spin. For example, the V1 particles may form an isotopic triplet, consisting of V1+, V10, and V1-. The τ+ and V40 may form an isotopic doublet, which we may call τ+ and τ0. 1963K. W. Ford World of Elem. Particles viii. 235 For a group of nucleons, a rotation of the total isotopic-spin vector in I space corresponds to changing from one nucleus to another without changing the total number of nucleons. Ibid., New particles..were found to come in closely linked groups, like proton and neutron. There were three pions which formed a triplet and could be described as three states of a single pion with one unit of isotopic spin. 1965Listener 2 Sept. 332/1 Abstract quantities known as ‘isotopic spin’ and ‘hyper⁓charge’. 1969D. H. Wilkinson Isospin i. 3 It is clear that Wigner gave the isotopic spin that name because it is a vector whose z-projection, ½(N - Z), distinguished one isotope from another along an isobaric multiplet. In fact Wigner often called Tz itself the isotopic spin and T ‘the total isotopic spin quantum number’. Others felt that a stronger case could be made to call the new quantum number the isobaric spin because its magnitude was constant along an isobaric multiplet.
c. Containing or being a less common or special isotope, e.g. as a label. Cf. isotope 1 b.
1942J. D. Stranathan ‘Particles’ of Mod. Physics v. 209 Heavy water..is one of the few compounds which can be produced in practically pure isotopic form. 1953Fruton & Simmonds Gen. Biochem. xxviii. 641 The administered isotopic glycine had ‘mixed’ with nonisotopic glycine already present in the body of the animal. 1954A. White et al. Princ. Biochem. xiv. 306 The isotopic material may be administered and, from the subsequent analyses for the appropriate isotope in the various tissues.., the distribution of the isotopic atom may be ascertained. 1958Oxf. Univ. Gaz. 5 June 1127/1 Studies on intermediary metabolism in whole animals using isotopic carbon.
d. Employing or depending on isotopes; obtained by such methods.
1956A. H. Compton Atomic Quest v. 326 As of 1956, three hundred American companies are using isotopic thickness gauges. 1962Newnes Conc. Encycl. Nucl. Energy 365/2 Another example of the application of the isotopic tracer technique..is furnished by the use of radio-active iron to investigate the economy of haemoglobin iron. 1969Bennison & Wright Geol. Hist. Brit. Isles ii. 26 While isotopic dating does provide a system of dating of this kind, giving dates in millions of years, it is too imprecise to be relevant to this problem. 1971I. G. Gass et al. Understanding the Earth ii. 42/1 Laboratory techniques for determining so-called radioisotope, isotopic or radiometric ages of rocks (which used to be erroneously called absolute ages) are extremely complex. |