On a Heuristic Point of View Concerning the Generation and Transformation of Light

§ 9. On the ionization of gases by ultraviolet light.Show the German source

We shall have to assume that in the ionization of a gas by ultraviolet light one absorbed light energy quantum is used for the ionization of one gas molecule.Show the German source From this it follows first that the ionization work (i.e., the work theoretically necessary for ionization) of a molecule cannot be greater than the energy of an absorbed effective light energy quantum.Show the German source If one denotes by $J$ the (theoretical) ionization work per gram-equivalent, then we must have:Show the German source $$R \beta \nu \geqq J .$$$R$Gas constant$\beta$Spectral constant B$\nu$Frequency of the light$J$Ionization work per gram-equivalentExplain this equationShow the German source According to Lenard’s measurements, however, the greatest effective wavelength for air is about $1{,}9 \cdot 10^{-5}$ cm, henceShow the German source $$R \beta \nu = 6{,}4 \cdot 10^{12} \text{ Erg} \geqq J .$$$R$Gas constant$\beta$Spectral constant B$\nu$Frequency of the light$J$Ionization work per gram-equivalentExplain this equationShow the German source

An upper limit for the ionization work is also obtained from the ionization voltages in rarefied gases.Show the German source According to J. Stark^[1)] the smallest ionization voltage measured (at platinum anodes) for air is about 10 volts.^[2)]Show the German source For $J$ there thus results the upper limit $9{,}6 \cdot 10^{12}$, which is nearly equal to the one just found.Show the German source There results yet another consequence, whose testing by experiment seems to me to be of great importance.Show the German source If each absorbed light energy quantum ionizes one molecule, then between the absorbed quantity of light $L$ and the number $j$ of gram-molecules ionized by it the following relation must hold:Show the German source $$j = \frac{L}{R \beta \nu} .$$$j$Ionized gram-molecules$L$Light energy absorbed$R$Gas constant$\beta$Spectral constant B$\nu$Frequency of the lightExplain this equationShow the German source This relation must, if our conception corresponds to reality, hold for every gas that (at the frequency in question) shows no appreciable absorption unaccompanied by ionization.Show the German source

Bern, 17 March 1905.Show the German source

(Received 18 March 1905.)Show the German source