Letter | Published:

Oscillator Strength of the Na2 1Σ—1Σ Transitions

Naturevolume 166pages191192 (1950) | Download Citation



WHILE the oscillator strengths (or ƒ-values) of various molecular electronic transitions are urgently required by astrophysicists, very few experimental or theoretical results are available. I have recently carried out a calculation for the ƒ-value of the 1Σ—1Σ transition of the sodium molecule based on the simple hydrogen-ion model. In this calculation the wave functions of the two states were represented by a simple linear combination of the appropriate atomic wave functions (these being taken as Slater-type functions with effective nuclear charge 2.2e and n* = 3). Taking the internuclear distance as 3.36 a0 (a0 is the radius of first Bohr orbit) and the wave-length of the electronic transition as 6812 A., the ƒ-value was found to be 0.26, corresponding to a mean life-time of 1.7 × 10−8 sec. No experimental measurement of this life-time has yet been made, but the value would not be expected to be widely different from the value for the blue-green system (1Σ — 1Π), which has approximately the same intensity. The life-time of this system was measured by Hupfeld1 and found to be 1.0 × 10−8 sec., which is of the same order as the theoretical result. Further results based on the hydrogen-ion and the hydrogen-molecule approximations will be reported in greater detail at a later date.

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  1. 1

    Hupfeld, H. H., Z. Phys., 54, 484 (1929).

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  1. Department of Astrophysics, Imperial College of Science and Technology, London, S.W.7



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