In 3d with V(|r|)

mi=m (reduced mass of nuclei measured in electron mass units)

                Equation 2.7 of Variance Minimization becomes

  (1.1)

Ground State

                Try         

                (1.2)

Equation (1.1) becomes

(1.3)

As in the one-d case a=Ö(m/2) cancels the variability of the variance, if V = r2,  leading to E=3/Ö(m2),  which is 3 times the zero point energy in 1 d.

                In the case that V is (r-c)2, the form for Y is more complicated.  It is ÑY×ÑY that cancels with V for r2 which is much more difficult to arrange in this case.

Excited State

In (1.1)try the form

 (2.1)

So that

(2.2)

Simplify

               (2.3)

If a-Ö(m/2) and V = r2, then E = 5/Ö(2m) -- as it should.  If V(r) minimizes at other than r = 0, then the 1/x from the first derivative will interact with the x when the ex coefficient is squared.

With Ylm

From Morse and Feshbach[1](2.5)

                    (2.6)

The operator[2]

(2.7)

So that

(2.8)

In Error! Reference source not found.try the form

 (2.9)

So that

(2.10)

In this case the components of the square are orthogonal so that

(2.11)

Then the process that led to the log terms can be reversed leading to

(2.12)

So that (2.11) becomes

(2.13)

Substituting -L2Y/r2 for Ñ2 from (2.7)

              (2.14)

Then using

      (2.15)

Try the form

(2.16)

So that

(2.17)

The del2 of log(r) is given by

               (2.18)

Del of log(r) is

               (2.19)

Del of r2 is

(2.20)

So that (2.17) becomes

     (2.21)

Collecting terms

                               (2.22)

This says that K=l, and for V=r2, a = Ö(m/2).  Note that the term rK is necessary. 

 

 



[1] P.M. Morse & H. Feshbach, Methods of Theoretical Physics, McGraw-Hill (1953) p. 116

[2] For example see E. Merzbacher, Quantum Mechanics, John Wiley (1961) section 9.2