diff options
Diffstat (limited to 'content/know/concept/electric-dipole-approximation')
-rw-r--r-- | content/know/concept/electric-dipole-approximation/index.pdc | 12 |
1 files changed, 6 insertions, 6 deletions
diff --git a/content/know/concept/electric-dipole-approximation/index.pdc b/content/know/concept/electric-dipole-approximation/index.pdc index 96b4fed..265babf 100644 --- a/content/know/concept/electric-dipole-approximation/index.pdc +++ b/content/know/concept/electric-dipole-approximation/index.pdc @@ -46,7 +46,7 @@ In an electromagnetic wave, $\vec{A}$ is oscillating sinusoidally in time and space as follows: $$\begin{aligned} - \vec{A}(\vec{r}, t) = \vec{A}_0 \exp\!(i \vec{k} \cdot \vec{r} - i \omega t) + \vec{A}(\vec{r}, t) = - i \vec{A}_0 \exp\!(i \vec{k} \cdot \vec{r} - i \omega t) \end{aligned}$$ The corresponding perturbative @@ -59,7 +59,7 @@ $$\begin{aligned} = \vec{E}_0 \exp\!(i \vec{k} \cdot \vec{r} - i \omega t) \end{aligned}$$ -Where $\vec{E}_0 = i \omega \vec{A}_0$. +Where $\vec{E}_0 = \omega \vec{A}_0$. Let us restrict ourselves to visible light, whose wavelength $2 \pi / k \approx 10^{-6} \:\mathrm{m}$. Meanwhile, an atomic orbital is on the order of $10^{-10} \:\mathrm{m}$, @@ -82,7 +82,7 @@ and the electron quantum-mechanically. Next, we want to convert $\hat{H}_1$ to use the electric field $\vec{E}$ instead of the potential $\vec{A}$. To do so, we rewrite the momemtum $\vec{P} = m \: \dv*{\vec{r}}{t}$ -and evaluate this in the [Heisenberg picture](/know/concept/heisenberg-picture/): +and evaluate this in the [interaction picture](/know/concept/interaction-picture/): $$\begin{aligned} \matrixel{2}{\dv*{\vec{r}}{t}}{1} @@ -95,15 +95,15 @@ $$\begin{aligned} Therefore, $\vec{P} / m = i \omega_0 \vec{r}$, where $\omega_0 \equiv (E_2 - E_1) / \hbar$ is the resonance frequency of the transition, -close to which we assume that $\vec{A}$ and $\vec{E}$ are oscillating. +close to which we assume that $\vec{A}$ and $\vec{E}$ are oscillating, i.e. $\omega \approx \omega_0$. We thus get: $$\begin{aligned} \hat{H}_1(t) &= - \frac{q}{m} \vec{P} \cdot \vec{A} - = - i q \omega_0 \vec{r} \cdot \vec{A}_0 \exp\!(- i \omega t) + = - (- i i) q \omega_0 \vec{r} \cdot \vec{A}_0 \exp\!(- i \omega t) \\ - &= - q \vec{r} \cdot \vec{E}_0 \exp\!(- i \omega t) + &\approx - q \vec{r} \cdot \vec{E}_0 \exp\!(- i \omega t) = - \vec{d} \cdot \vec{E}_0 \exp\!(- i \omega t) \end{aligned}$$ |