Find Expectation Value of x for \psi(x,t)

[ehrenfest]

I am trying to find <x> for

$$\psi(x,t) = A exp\left(-|x|/L - i*E*t/\hbar\right)$$

I found the normalization factor of 1/L and I took

$$\int_{-\infty}^{\infty}\left( x * exp(|x|/L) \right)$$ in two

integrals however I got as a final result:

$$L * -\infty * exp(-\infty/ L) - L * \infty * exp( - \infty /L)$$

Is that 0?

 

[Sojourner01]

I believe your answer tends towards zero:

$$L * -\infty * exp(-\infty/ L) - L * \infty * exp( - \infty /L) = -2 * L * \infty * exp(-\infty/ L) -> -\infty/exp(\infty) -> 0$$

 

[ehrenfest]

I see. That's the problem with throwing around infinities instead of using limits.