21 FIG. 7: (Position dependent mass case). Plot of the normalized wave function Re [ u$_{2}$ ] (left panel) and of the probability density (right panel) for E = 0 . 97248 (highest excited state). The model parameters are the same as those of Figure 5 except for W which now is W = 3. FIG. 6: The case of constant mass. Upper panel: plot of the normalized wave function Re [ u$_{1}$ ] and probability density for E = − 0 . 759003 (lowest energy bound state); Lower panel: the same but for E = +0 . 7888942 (highest excited state). The model parameters are the same as those of Figure 5: m$_{0}$ = 1, W = 2, a = 10 and L = 2. -$_{5}$ 5 x -$_{0.3}$ -$_{0.2}$ -$_{0.1}$ 0.1 0.2 0.3 $_{Re}$@$_{u}$$_{2}$ H$_{x}$LD -$_{5}$ 0 5 x 0.02 0.04 0.06 0.08 0.10 0.12 r H$_{x}$L -$_{6}$ -$_{4}$ -$_{2}$ 2 4 6 x 0.05 0.10 0.15 0.20 $_{Re}$@$_{u}$$_{1}$ H$_{x}$LD -$_{6}$ -$_{4}$ -$_{2}$ 2 4 6 x 0.1 0.2 0.3 0.4 r H$_{x}$L -$_{6}$ -$_{4}$ -$_{2}$ 2 4 6 x -$_{0.4}$ -$_{0.2}$ 0.2 0.4 $_{Re}$@$_{u}$$_{1}$ H$_{x}$LD -$_{6}$ -$_{4}$ -$_{2}$ 2 4 6 x 0.05 0.10 0.15 0.20 r H$_{x}$L