Talk:DWBA

DWBA Equation in thin film

Using the notation $T_{i}=T(\alpha _{i})$ for compactness, the DWBA equation inside a thin film can be written:

${\begin{aligned}I_{d}(q_{z})&=|T_{i}T_{f}F(+Q_{z1})+T_{i}R_{f}F(-Q_{z2})+R_{i}T_{f}F(+Q_{z2})+R_{i}R_{f}F(-Q_{z1})|^{2}\\\end{aligned}}$

Expansion (incorrect)

WARNING: This incorrectly ignores the complex components.

Terms

If one expands the $|...|^{2}$ of the DWBA, one obtains 16 terms:

Failed to parse (MathML with SVG or PNG fallback (recommended for modern browsers and accessibility tools): Invalid response ("Math extension cannot connect to Restbase.") from server "https://wikimedia.org/api/rest_v1/":): {\displaystyle \begin{matrix} & (T_i T_f) & (T_i R_f) & (R_i T_f) & (R_i R_f) \\ (T_i T_f) & T_i^2T_f^2 & T_i^2 T_f R_f & T_iR_iT_f^2 & T_iR_iT_fR_f \\ (T_i R_f) & T_i^2T_fR_f & T_i^2R_f^2 & T_iR_iT_fR_f & T_iR_iR_f^2 \\ (R_i T_f) & T_iR_iT_f^2 & T_iR_iT_fR_f & R_i^2T_f^2 & R_i^2T_fR_f \\ (R_i R_f) & T_iR_iT_fR_f & T_iR_iR_f^2 & R_i^2T_fR_f & R_i^2R_f^2 \\ \end{matrix} }

Equation

The equation can thus be expanded as:

${\begin{aligned}I_{d}(q_{z})&=|T_{i}T_{f}F(+Q_{z1})+T_{i}R_{f}F(-Q_{z2})+R_{i}T_{f}F(+Q_{z2})+R_{i}R_{f}F(-Q_{z1})|^{2}\\&{\begin{aligned}=\,\,&T_{i}^{2}T_{f}^{2}|F(+Q_{z1})|^{2}&&+T_{i}^{2}T_{f}R_{f}F(+Q_{z1})F(-Q_{z2})\\&&&+T_{i}R_{i}T_{f}^{2}F(+Q_{z1})F(+Q_{z2})+T_{i}R_{i}T_{f}R_{f}F(+Q_{z1})F(-Q_{z1})\\&+T_{i}^{2}R_{f}^{2}|F(-Q_{z2})|^{2}&&+T_{i}^{2}T_{f}R_{f}F(+Q_{z1})F(-Q_{z2})\\&&&+T_{i}R_{i}T_{f}R_{f}F(+Q_{z2})F(-Q_{z2})+T_{i}R_{i}R_{f}^{2}F(-Q_{z1})F(-Q_{z2})\\&+R_{i}^{2}T_{f}^{2}|F(+Q_{z2})|^{2}&&+T_{i}R_{i}T_{f}^{2}F(+Q_{z1})F(+Q_{z2})\\&&&+T_{i}R_{i}T_{f}R_{f}F(+Q_{z2})F(-Q_{z2})+R_{i}^{2}T_{f}R_{f}F(-Q_{z1})F(+Q_{z2})\\&+R_{i}^{2}R_{f}^{2}|F(-Q_{z1})|^{2}&&+T_{i}R_{i}T_{f}R_{f}F(+Q_{z1})F(-Q_{z1})\\&&&+T_{i}R_{i}R_{f}^{2}F(-Q_{z1})F(-Q_{z2})+R_{i}^{2}T_{f}R_{f}F(-Q_{z1})F(+Q_{z2})\\\end{aligned}}\\\end{aligned}}$

Simplification

We can rearrange to:

Failed to parse (MathML with SVG or PNG fallback (recommended for modern browsers and accessibility tools): Invalid response ("Math extension cannot connect to Restbase.") from server "https://wikimedia.org/api/rest_v1/":): {\displaystyle \begin{align} I_d(q_{z}) = \,\, & T_i^2 T_f^2 | F(+Q_{z1}) |^2 + T_i^2 R_f^2 | F(-Q_{z2}) |^2 + R_i^2 T_f^2 | F(+Q_{z2}) |^2 + R_i^2 R_f^2 | F(-Q_{z1}) |^2 \\ & + T_i^2 T_f R_f F(+Q_{z1})F(-Q_{z2}) \\ & + T_i R_i T_f^2 F(+Q_{z1})F(+Q_{z2}) + T_i R_i T_f R_f F(+Q_{z1}) F(-Q_{z1}) \\ & + T_i^2T_fR_f F(+Q_{z1}) F(-Q_{z2}) \\ & + T_i R_i T_f R_f F(+Q_{z2})F(-Q_{z2}) + T_i R_i R_f^2 F(-Q_{z1}) F(-Q_{z2}) \\ & + T_i R_i T_f^2 F(+Q_{z1}) F(+Q_{z2}) \\ & + T_i R_i T_f R_f F(+Q_{z2})F(-Q_{z2}) + R_i^2 T_f R_f F(-Q_{z1}) F(+Q_{z2}) \\ & + T_i R_i T_f R_f F(+Q_{z1}) F(-Q_{z1}) \\ & + T_i R_i R_f^2 F(-Q_{z1})F(-Q_{z2}) + R_i^2 T_f R_f F(-Q_{z1}) F(+Q_{z2}) \\ = \,\, & T_i^2 T_f^2 | F(+Q_{z1}) |^2 + T_i^2 R_f^2 | F(-Q_{z2}) |^2 + R_i^2 T_f^2 | F(+Q_{z2}) |^2 + R_i^2 R_f^2 | F(-Q_{z1}) |^2 \\ & + 2 \times T_i^2T_fR_f F(+Q_{z1})F(-Q_{z2}) \\ & + 2 \times T_iR_iT_f^2 F(+Q_{z1})F(+Q_{z2}) \\ & + 2 \times T_i R_i T_f R_f [ F(+Q_{z1})F(-Q_{z1}) + F(+Q_{z2})F(-Q_{z2}) ] \\ & + 2 \times T_iR_iR_f^2 F(-Q_{z1})F(-Q_{z2}) \\ & + 2 \times R_i^2T_fR_fx F(-Q_{z1})F(+Q_{z2}) \\ = \,\, & T_i^2 T_f^2 | F(+Q_{z1}) |^2 + T_i^2 R_f^2 | F(-Q_{z2}) |^2 + R_i^2 T_f^2 | F(+Q_{z2}) |^2 + R_i^2 R_f^2 | F(-Q_{z1}) |^2 \\ & + 2 \times T_i^2T_fR_f F(+Q_{z1})F(-Q_{z2}) + 2 \times T_iR_iT_f^2 F(+Q_{z1})F(+Q_{z2}) \\ & + 2 \times T_i R_i T_f R_f [ F(+Q_{z1})F(-Q_{z1}) + F(+Q_{z2})F(-Q_{z2}) ] \\ & + 2 \times T_iR_iR_f^2 F(-Q_{z1})F(-Q_{z2}) + 2 \times R_i^2T_fR_fx F(-Q_{z1})F(+Q_{z2}) \\ \end{align} }

We can rewrite in a more compact form using the notation Failed to parse (MathML with SVG or PNG fallback (recommended for modern browsers and accessibility tools): Invalid response ("Math extension cannot connect to Restbase.") from server "https://wikimedia.org/api/rest_v1/":): {\displaystyle T_i = T(\alpha_i)} and $F_{+1}=F(+Q_{z1})$:

Failed to parse (MathML with SVG or PNG fallback (recommended for modern browsers and accessibility tools): Invalid response ("Math extension cannot connect to Restbase.") from server "https://wikimedia.org/api/rest_v1/":): {\displaystyle \begin{align} I_d(q_{z}) = \,\, & T_i^2 T_f^2 | F_{+1} |^2 + T_i^2 R_f^2 | F_{-2} |^2 + R_i^2 T_f^2 | F_{+2} |^2 + R_i^2 R_f^2 | F_{-1} |^2 \\ & + 2 \times T_i^2T_fR_f F_{+1}F_{-2} + 2 \times T_iR_iT_f^2 F_{+1}F_{+2} \\ & + 2 \times T_i R_i T_f R_f [ F_{+1}F_{-1} + F_{+2}F_{-2} ] \\ & + 2 \times T_iR_iR_f^2 F_{-1}F_{-2} + 2 \times R_i^2T_fR_f F_{-1}F_{+2} \end{align} }

Expansion

Terms

If one expands the Failed to parse (MathML with SVG or PNG fallback (recommended for modern browsers and accessibility tools): Invalid response ("Math extension cannot connect to Restbase.") from server "https://wikimedia.org/api/rest_v1/":): {\displaystyle |...|^2} of the DWBA, one obtains 16 terms:

Failed to parse (MathML with SVG or PNG fallback (recommended for modern browsers and accessibility tools): Invalid response ("Math extension cannot connect to Restbase.") from server "https://wikimedia.org/api/rest_v1/":): {\displaystyle \begin{matrix} & (T_i^* T_f^*) & (T_i^* R_f^*) & (R_i^* T_f^*) & (R_i^* R_f^*) \\ (T_i T_f) & T_i T_i^* T_f T_f^* & T_i T_i^* T_f R_f^* & T_i R_i^* T_f T_f^* & T_i R_i^* T_f R_f^* \\ (T_i R_f) & T_i T_i^* T_f^* R_f & T_i T_i^* R_f R_f^* & T_i R_i^* T_f^* R_f & T_i R_i^* R_f R_f^* \\ (R_i T_f) & T_i^* R_i T_f T_f^* & T_i^* R_i T_f R_f^* & R_i R_i^* T_f T_f^* & R_i R_i^* T_f R_f^* \\ (R_i R_f) & T_i^* R_i T_f^* R_f & T_i^* R_i R_f R_f^* & R_i R_i^* T_f^* R_f & R_i R_i^* R_f R_f^* \\ \end{matrix} }

${\begin{matrix}&(T_{i}^{*}T_{f}^{*})&(T_{i}^{*}R_{f}^{*})&(R_{i}^{*}T_{f}^{*})&(R_{i}^{*}R_{f}^{*})\\(T_{i}T_{f})&|T_{i}T_{f}|^{2}&|T_{i}|^{2}T_{f}R_{f}^{*}&T_{i}R_{i}^{*}|T_{f}|^{2}&T_{i}R_{i}^{*}T_{f}R_{f}^{*}\\(T_{i}R_{f})&|T_{i}|^{2}T_{f}^{*}R_{f}&|T_{i}R_{f}|^{2}&T_{i}R_{i}^{*}T_{f}^{*}R_{f}&T_{i}R_{i}^{*}|R_{f}|^{2}\\(R_{i}T_{f})&T_{i}^{*}R_{i}|T_{f}|^{2}&T_{i}^{*}R_{i}T_{f}R_{f}^{*}&|R_{i}T_{f}|^{2}&|R_{i}|^{2}T_{f}R_{f}^{*}\\(R_{i}R_{f})&T_{i}^{*}R_{i}T_{f}^{*}R_{f}&T_{i}^{*}R_{i}|R_{f}|^{2}&|R_{i}|^{2}T_{f}^{*}R_{f}&|R_{i}R_{f}|^{2}\\\end{matrix}}$

Equation

We take advantage of a more compact form using the notation $T_{i}=T(\alpha _{i})$ and $F_{+1}=F(+Q_{z1})$. The DWBA equation can thus be expanded as:

${\begin{aligned}I_{d}(q_{z})&=|T_{i}T_{f}F_{+1}+T_{i}R_{f}F_{-2}+R_{i}T_{f}F_{+2}+R_{i}R_{f}F_{-1}|^{2}\\&{\begin{aligned}=\,\,&|T_{i}T_{f}|^{2}|F_{+1}|^{2}&&+T_{i}^{2}T_{f}R_{f}F_{+1}F_{-2}\\&&&+T_{i}R_{i}T_{f}^{2}F_{+1}F_{+2}+T_{i}R_{i}T_{f}R_{f}F_{+1}F_{-1}\\&+|T_{i}R_{f}|^{2}|F_{-2}|^{2}&&+T_{i}^{2}T_{f}R_{f}F_{+1}F_{-2}\\&&&+T_{i}R_{i}T_{f}R_{f}F_{+2}F_{-2}+T_{i}R_{i}R_{f}^{2}F_{-1}F_{-2}\\&+|R_{i}T_{f}|^{2}|F_{+2}|^{2}&&+T_{i}R_{i}T_{f}^{2}F_{+1}F_{+2}\\&&&+T_{i}R_{i}T_{f}R_{f}F_{+2}F_{-2}+R_{i}^{2}T_{f}R_{f}F_{-1}F_{+2}\\&+|R_{i}R_{f}|^{2}|F_{-1}|^{2}&&+T_{i}R_{i}T_{f}R_{f}F_{+1}F_{-1}\\&&&+T_{i}R_{i}R_{f}^{2}F_{-1}F_{-2}+R_{i}^{2}T_{f}R_{f}F_{-1}F_{+2}\\\end{aligned}}\\\end{aligned}}$

Breaking into components

The experimental data $I_{d}(q_{z})$ can be broken into contributions from the transmitted channel $I_{Tc}(qz)$ and reflected channel $I_{Rc}(qz)$:

${\begin{aligned}I_{d}(q_{z})&=[|T_{i}T_{f}|^{2}+|R_{i}R_{f}|^{2}]I_{Tc}(q_{z})+[|T_{i}R_{f}|^{2}+|R_{i}T_{f}|^{2}]I_{Rc}(q_{z})\\&=|Tc|^{2}I_{Tc}(q_{z})+|Rc|^{2}I_{Rc}(q_{z})\\\end{aligned}}$

We define the ratio between the channels to be:

${\begin{aligned}w&={\frac {I_{Tc}(q_{z})}{I_{Tc}(q_{z})+I_{Rc}(q_{z})}}\end{aligned}}$

Such that one can compute the two components from:

${\begin{aligned}I_{d}(q_{z})&=|Tc|^{2}(I_{Tc}(q_{z}))+|Rc|^{2}(I_{Rc}(q_{z}))\\I_{d}(q_{z})&=|Tc|^{2}(I_{Tc}(q_{z}))+|Rc|^{2}\left({\frac {I_{Tc}(q_{z})-wI_{Tc}(q_{z})}{w}}\right)\\I_{d}(q_{z})&=I_{Tc}(q_{z})\times \left(|Tc|^{2}+|Rc|^{2}{\frac {1}{w}}-|Rc|^{2}{\frac {w}{w}}\right)\\I_{Tc}(q_{z})&={\frac {I_{d}(q_{z})}{|Tc|^{2}+{\frac {|Rc|^{2}}{w}}-|Rc|^{2}}}\\\end{aligned}}$

and:

${\begin{aligned}I_{Rc}(q_{z})&={\frac {I_{d}(q_{z})-|Tc|^{2}I_{Tc}(q_{z})}{|Rc|^{2}}}\end{aligned}}$