314 1933 E SCHRODINGER of alpha rays done by Rutherford and Chadwick. Instead of the electrons we introduce hypothetical waves, whose wavelengths are left entirely open, because we know nothing about them yet. This leaves a letter, say a, in dicating a still unknown figure, in our calculation. We are, however, used to this in such calculations and it does not prevent us from calculating that the nucleus of the atom must produce a kind of diffraction phenomenon in these waves, similarly as a minute dust particle does in light waves. Analo- gously, it follows that there is a close relationship between the extent of the area of interference with which the nucleus surrounds itself and the wave- length, and that the two are of the same order of magnitude. What this is we have had to leave open; but the most important step now follows: we identify the area of interference, the diffraction halo, with the atom; we assert that the atom in reality is merely the diffraction phenomenon of an electron wave cap- tured us it were by the nucleus of the atom It is no longer a matter of chance that the size of the atom and the wavelength are of the same order of magni- tude it is a matter of course. We know the numerical value of neither because we still have in our calculation the one unknown constant which we called a. There are two possible ways of determining it, which provide a mutual check on one another. first we can so select it that the manifesta tions of life of the atom, above all the spectrum lines emitted, come out correctly quantitatively; these can after all be measured very accurately Secondly, we can select a in a manner such that the diffraction halo acquires the size required for the atom. These two determinations of a(of which the second is admittedly far more imprecise because "size of the atom"is no clearly defined term)are in complete agreement with one another. Thirdly, and lastly, we can remark that the constant remaining unknown, physically speaking, does not in fact have the dimension of a length, but of an action, i.e. energy X time. It is then an obvious step to substitute for it the numerical alue of Plancks universal quantum of action, which is accurately known from the laws of heat radiation It will be seen that we return, with the full now considerable accuracy, to the first(most accurate) determination Quantitatively speaking, the theory therefore manages with a minimum of new assumptions. It contains a single available constant, to which a numerical value familiar from the older quantum theory must be given, first to attribute to the diffraction halos the right size so that they can be reasonably identified with the atoms, and secondly, to evaluate quantitative- ly and correctly all the manifestations of life of the atom, the light radiated by it, the ionization energy, etc314 1933 E. SCHRÖDINGER of alpha rays done by Rutherford and Chadwick. Instead of the electrons we introduce hypothetical waves, whose wavelengths are left entirely open, because we know nothing about them yet. This leaves a letter, say a, in￾dicating a still unknown figure, in our calculation. We are, however, used to this in such calculations and it does not prevent us from calculating that the nucleus of the atom must produce a kind of diffraction phenomenon in these waves, similarly as a minute dust particle does in light waves. Analo￾gously, it follows that there is a close relationship between the extent of the area of interference with which the nucleus surrounds itself and the wave￾length, and that the two are of the same order of magnitude. What this is, we have had to leave open; but the most important step now follows: we identify the area of interference, the diffraction halo, with the atom; we assert that the atom in reality is merely the diffraction phenomenon of an electron wave cap￾tured us it were by the nucleus of the atom. It is no longer a matter of chance that the size of the atom and the wavelength are of the same order of magni￾tude: it is a matter of course. We know the numerical value of neither, because we still have in our calculation the one unknown constant, which we called a. There are two possible ways of determining it, which provide a mutual check on one another. First, we can so select it that the manifesta￾tions of life of the atom, above all the spectrum lines emitted, come out correctly quantitatively; these can after all be measured very accurately. Secondly, we can select a in a manner such that the diffraction halo acquires the size required for the atom. These two determinations of a (of which the second is admittedly far more imprecise because "size of the atom" is no clearly defined term) are in complete agreement with one another. Thirdly, and lastly, we can remark that the constant remaining unknown, physically speaking, does not in fact have the dimension of a length, but of an action, i.e. energy x time. It is then an obvious step to substitute for it the numerical value of Planck’s universal quantum of action, which is accurately known from the laws of heat radiation. It will be seen that we return, with the full, now considerable accuracy, to the first (most accurate) determination. Quantitatively speaking, the theory therefore manages with a minimum of new assumptions. It contains a single available constant, to which a numerical value familiar from the older quantum theory must be given, first to attribute to the diffraction halos the right size so that they can be reasonably identified with the atoms, and secondly, to evaluate quantitative￾ly and correctly all the manifestations of life of the atom, the light radiated by it, the ionization energy, etc