Letter | Published:

Predissociation and Pressure Effects in the Band Spectrum of Aluminium Hydride

Nature volume 131, pages 470471 (01 April 1933) | Download Citation

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Abstract

BY the aid of graphical methods1, we have constructed the potential curves Vj(r) for different rotational states of 1II in aluminium hydride. From estimations on the line width of the diffuse lines in the 1II; 1 band system, we were able to extend our constructions to wide nuclear spacing (r 3 × 108 cm.) as shown in Fig. 1. Reproducing the curve we found, that even now a potential barrier remains in 1II, the height of which is 400 cm.1, as related to the limit of dissociation. This result appears somewhat surprising, as in the few cases hitherto investigated (hydrogen, mercury hydride, etc.) a smooth approach of the potential curves to the limit of dissociation has been assumed. We are not in the position to distinguish between the alternatives, whether this barrier is a feature of the 1II–state itself or produced by the intersection of some unknown and repulsive 1II*;–state, as suggested in Fig. 1. In the latter case, the actual 1II–curve should be correlated to some excited state in the Al atom as already suggested by Kronig2, although for other reasons. In any event, by this construction the level scheme of AlH has been related to that of the Al atom, the position of the level = 0, J = 0 in 1II situated 1400 ± 50 cm1 below the limit of dissociation. Incidentally, it may be mentioned that some interesting cases of perturbations and predissociations in the excited 1 and 1 states4 are readily explained hereby.

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References

  1. 1.

    , Z. Phys., 73, 376 ; 1931. ibid., 80, 517; 1933.

  2. 2.

    , Z. Phys., 62, 300; 1930. Regarding the constructions of the potential curves of AlH we made use of a more exact relation between the line width and the potential barrier, recently developed by G. Müller, Z. Phys., 79, 595; 1932.

  3. 3.

    The general theory of inelastic collisions has been thoroughly treated by G. Gamow in his book "Atomic Nuclei and Radioactivity", Oxford University Press, 1931.

  4. 4.

    , and , Z. Phys., 59, 540; 1930.

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Affiliations

  1. Laboratory of Physics, University of Stockholm. Feb. 8.

    • ERIK HULTHÉN
    •  & RAGNAR RYDBERG

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DOI

https://doi.org/10.1038/131470b0

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