Abstract: The well-known variation method of calculating the total energy of a two-electron atom is generalized to the case of any set of quantum numbers of electrons in spaces of three or fewer dimensions, yielding the corresponding expressions for energy and screening constant. From these results, the particular cases of the basic and the lowest excited states follow, as earlier considered by us and other authors. We clarify the correct use of these results. Moreover, we generalize the standard relations connecting the average values of kinetic and potential energy with the total energy of an electron in a nucleus field in three dimension for any quantum state and extend it to subspaces of one and two dimensions in a three-dimensional space. The results of this work could be a useful addition to a university course on quantum mechanics.
Abstract: The well-known variation method of calculating the total energy of a two-electron atom is generalized to the case of any set of quantum numbers of electrons in spaces of three or fewer dimensions, yielding the corresponding expressions for energy and screening constant. From these results, the particular cases of the basic and the lowest excited states follow, as earlier considered by us and other authors. We clarify the correct use of these results. Moreover, we generalize the standard relations connecting the average values of kinetic and potential energy with the total energy of an electron in a nucleus field in three dimension for any quantum state and extend it to subspaces of one and two dimensions in a three-dimensional space. The results of this work could be a useful addition to a university course on quantum mechanics.
The total energy of a particle (e.g., an electron in an atom, a free electron, an electron in an electric field, a conduction electron in a solid) is the sum of the 1 2 potential and kinetic energies. Expressed in terms of momentum p, and mass m, this is stated: mvp since Considering a one-dimensional case, Energy equation let t iE x ip i2 = 1 Now, the potential energy, V, may depend upon the position and time, and so in general, V = V(x,t).
In the previous chapter we saw that for a particle in a one-dimensional potential well, physically acceptable solutions to the one-dimensional Schro¨dinger equation are possible only for particular discrete values of the total energy. Moreover, in the case of an electron in a well of atomic dimensions, the spacings between these energy levels are in qualitative agreement with the separations experimentally observed in atoms; we also interpreted the square of the wave function as a probability distribution for the position of the particle. These ideas led us to phenomena, such as quantum-mechanical tunnelling, that have been observed experimentally. The real world, however, is three-dimensional and, although one-dimensional examples often provide useful insights and analogies, we shall have to extend our theory into three dimensions before we can make quantitative predictions of most experimental results. In the present chapter, therefore, we shall set up the three-dimensional Schro¨dinger equation and obtain its solutions in a number of cases, culminating in a discussion of the hydrogen atom where we shall find that theory and experiment agree to a remarkable degree of accuracy.
The total energy of a particle (e.g., an electron in an atom, a free electron, an electron in an electric field, a conduction electron in a solid) is the sum of the V m p E Vpv VmvE potential and kinetic energies. Expressed in terms of momentum p, and mass m, this is stated: mvp since hfE h k f Considering movement in one dimension only, let t iE x ip i2 = 1 Now, the potential energy, V, may depend upon the position and time, and so in general, V = V(x,t).
With the use of the known solution of the Schrödinger equation for an electron in the nucleus field in the polar coordinates, the energy of a “two-dimensional” two-electron atom in the ground state, as well as its single ionization energy, has been calculated both in perturbation theory and with an almost century-old method of variation of the parameter Z in a trial wavefunction of the ground state. Since such two-dimensional atoms, e.g., helium atoms, can in principle be implemented in experiments by “freezing” of one degree of freedom in the phase of Bose–Einstein condensate, the conclusions made in this work can be tested. Fundamental features of the calculation of the energy of “one-dimensional” two-electron atoms and the formation of their Bose–Einstein condensate have also been discussed. The results obtained in this work coincide in a number of particular cases with the results obtained in a previous work, where some results were absent.
In an earlier paper appropriate limiting procedure is discussed in a general way for quantum mechanical energy eigenfunctions (one-dimensional bound states) — a single interpretational postulate leading smoothly to entire compatible classical objective description without facing any contradiction. The method is consistently extended to two- and three-dimensional cases and it is interesting to note that results of earlier study on the classical limit of the radial distribution function of hydrogen atom are easily obtained as special cases of our analysis.
In this second chapter we will review the basic mathematical and physical facts about quantum mechanics and establish physical units and notation. Those readers already familiar with the subject can safely jump to the next chapter. An attempt has been made to make the presentation in this chapter as elementary as possible, and yet present the basic facts that will be needed later. There are many beautiful and important topics which will not be touched upon such as self-adjointness of Schrödinger operators, the general mathematical structure of quantum mechanics and the like. These topics are well described in other works, e.g.. Much of the following can be done in a Euclidean space of arbitrary dimension, but in this chapter the dimension of the Euclidean space is taken to be three-which is the physical case-unless otherwise stated. We do this to avoid confusion and, occasionally, complications that arise in the computation of mathematical constants. The interested reader can easily generalize what is done here to the R d , d > 3 case. Likewise, in the next chapters we mostly consider N particles, with spatial coordinates in R 3 , so that the total spatial dimension is 3 N . A Brief Review of the Connection Between Classical and Quantum Mechanics Considering the range of validity of quantum mechanics, it is not surprising that its formulation is more complicated and abstract than classical mechanics. Nevertheless, classical mechanics is a basic ingredient for quantum mechanics. One still talks about position, momentum and energy which are notions from Newtonian mechanics.