10.5: Appendix - Jacobians
- Page ID
- 372723
\( \newcommand{\vecs}[1]{\overset { \scriptstyle \rightharpoonup} {\mathbf{#1}} } \)
\( \newcommand{\vecd}[1]{\overset{-\!-\!\rightharpoonup}{\vphantom{a}\smash {#1}}} \)
\( \newcommand{\id}{\mathrm{id}}\) \( \newcommand{\Span}{\mathrm{span}}\)
( \newcommand{\kernel}{\mathrm{null}\,}\) \( \newcommand{\range}{\mathrm{range}\,}\)
\( \newcommand{\RealPart}{\mathrm{Re}}\) \( \newcommand{\ImaginaryPart}{\mathrm{Im}}\)
\( \newcommand{\Argument}{\mathrm{Arg}}\) \( \newcommand{\norm}[1]{\| #1 \|}\)
\( \newcommand{\inner}[2]{\langle #1, #2 \rangle}\)
\( \newcommand{\Span}{\mathrm{span}}\)
\( \newcommand{\id}{\mathrm{id}}\)
\( \newcommand{\Span}{\mathrm{span}}\)
\( \newcommand{\kernel}{\mathrm{null}\,}\)
\( \newcommand{\range}{\mathrm{range}\,}\)
\( \newcommand{\RealPart}{\mathrm{Re}}\)
\( \newcommand{\ImaginaryPart}{\mathrm{Im}}\)
\( \newcommand{\Argument}{\mathrm{Arg}}\)
\( \newcommand{\norm}[1]{\| #1 \|}\)
\( \newcommand{\inner}[2]{\langle #1, #2 \rangle}\)
\( \newcommand{\Span}{\mathrm{span}}\) \( \newcommand{\AA}{\unicode[.8,0]{x212B}}\)
\( \newcommand{\vectorA}[1]{\vec{#1}} % arrow\)
\( \newcommand{\vectorAt}[1]{\vec{\text{#1}}} % arrow\)
\( \newcommand{\vectorB}[1]{\overset { \scriptstyle \rightharpoonup} {\mathbf{#1}} } \)
\( \newcommand{\vectorC}[1]{\textbf{#1}} \)
\( \newcommand{\vectorD}[1]{\overrightarrow{#1}} \)
\( \newcommand{\vectorDt}[1]{\overrightarrow{\text{#1}}} \)
\( \newcommand{\vectE}[1]{\overset{-\!-\!\rightharpoonup}{\vphantom{a}\smash{\mathbf {#1}}}} \)
\( \newcommand{\vecs}[1]{\overset { \scriptstyle \rightharpoonup} {\mathbf{#1}} } \)
\( \newcommand{\vecd}[1]{\overset{-\!-\!\rightharpoonup}{\vphantom{a}\smash {#1}}} \)
\(\newcommand{\avec}{\mathbf a}\) \(\newcommand{\bvec}{\mathbf b}\) \(\newcommand{\cvec}{\mathbf c}\) \(\newcommand{\dvec}{\mathbf d}\) \(\newcommand{\dtil}{\widetilde{\mathbf d}}\) \(\newcommand{\evec}{\mathbf e}\) \(\newcommand{\fvec}{\mathbf f}\) \(\newcommand{\nvec}{\mathbf n}\) \(\newcommand{\pvec}{\mathbf p}\) \(\newcommand{\qvec}{\mathbf q}\) \(\newcommand{\svec}{\mathbf s}\) \(\newcommand{\tvec}{\mathbf t}\) \(\newcommand{\uvec}{\mathbf u}\) \(\newcommand{\vvec}{\mathbf v}\) \(\newcommand{\wvec}{\mathbf w}\) \(\newcommand{\xvec}{\mathbf x}\) \(\newcommand{\yvec}{\mathbf y}\) \(\newcommand{\zvec}{\mathbf z}\) \(\newcommand{\rvec}{\mathbf r}\) \(\newcommand{\mvec}{\mathbf m}\) \(\newcommand{\zerovec}{\mathbf 0}\) \(\newcommand{\onevec}{\mathbf 1}\) \(\newcommand{\real}{\mathbb R}\) \(\newcommand{\twovec}[2]{\left[\begin{array}{r}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\ctwovec}[2]{\left[\begin{array}{c}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\threevec}[3]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\cthreevec}[3]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\fourvec}[4]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\cfourvec}[4]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\fivevec}[5]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\cfivevec}[5]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\mattwo}[4]{\left[\begin{array}{rr}#1 \amp #2 \\ #3 \amp #4 \\ \end{array}\right]}\) \(\newcommand{\laspan}[1]{\text{Span}\{#1\}}\) \(\newcommand{\bcal}{\cal B}\) \(\newcommand{\ccal}{\cal C}\) \(\newcommand{\scal}{\cal S}\) \(\newcommand{\wcal}{\cal W}\) \(\newcommand{\ecal}{\cal E}\) \(\newcommand{\coords}[2]{\left\{#1\right\}_{#2}}\) \(\newcommand{\gray}[1]{\color{gray}{#1}}\) \(\newcommand{\lgray}[1]{\color{lightgray}{#1}}\) \(\newcommand{\rank}{\operatorname{rank}}\) \(\newcommand{\row}{\text{Row}}\) \(\newcommand{\col}{\text{Col}}\) \(\renewcommand{\row}{\text{Row}}\) \(\newcommand{\nul}{\text{Nul}}\) \(\newcommand{\var}{\text{Var}}\) \(\newcommand{\corr}{\text{corr}}\) \(\newcommand{\len}[1]{\left|#1\right|}\) \(\newcommand{\bbar}{\overline{\bvec}}\) \(\newcommand{\bhat}{\widehat{\bvec}}\) \(\newcommand{\bperp}{\bvec^\perp}\) \(\newcommand{\xhat}{\widehat{\xvec}}\) \(\newcommand{\vhat}{\widehat{\vvec}}\) \(\newcommand{\uhat}{\widehat{\uvec}}\) \(\newcommand{\what}{\widehat{\wvec}}\) \(\newcommand{\Sighat}{\widehat{\Sigma}}\) \(\newcommand{\lt}{<}\) \(\newcommand{\gt}{>}\) \(\newcommand{\amp}{&}\) \(\definecolor{fillinmathshade}{gray}{0.9}\)Appendix: Jacobians
A.1. 3D to 1D
A Jacobian is a mathematical entity used to switch partials inside an integral. For the case of velocity in three dimensions being converted into spherical coordinates, where \(v\) is the net velocity and akin to a sphere’s radius:
\[\partial v_x\cdot \partial v_y\cdot \partial v_z=\left|\frac{\partial (v_x,v_y,v_z)}{\partial (v,\theta ,\phi )}\right|\cdot \partial v\cdot \partial \phi \cdot \partial \theta =v^2\cdot
Callstack:
at (Bookshelves/Physical_and_Theoretical_Chemistry_Textbook_Maps/Free_Energy_1e_(Snee)/10:_The_Kinetic_Theory_of_Gas/10.05:_Appendix), /content/body/div[2]/p[2]/span, line 1, column 1
To evaluate the above, we should have some idea how to convert v\({}_{x}\) v\({}_{y}\) v\({}_{z}\) into spherical coordinates to begin with. It’s just a lesson in geometry:
\[v_x=v\cdot
Callstack:
at (Bookshelves/Physical_and_Theoretical_Chemistry_Textbook_Maps/Free_Energy_1e_(Snee)/10:_The_Kinetic_Theory_of_Gas/10.05:_Appendix), /content/body/div[2]/p[4]/span[1], line 1, column 1
Callstack:
at (Bookshelves/Physical_and_Theoretical_Chemistry_Textbook_Maps/Free_Energy_1e_(Snee)/10:_The_Kinetic_Theory_of_Gas/10.05:_Appendix), /content/body/div[2]/p[4]/span[2], line 1, column 1
Callstack:
at (Bookshelves/Physical_and_Theoretical_Chemistry_Textbook_Maps/Free_Energy_1e_(Snee)/10:_The_Kinetic_Theory_of_Gas/10.05:_Appendix), /content/body/div[2]/p[4]/span[3], line 1, column 1
Callstack:
at (Bookshelves/Physical_and_Theoretical_Chemistry_Textbook_Maps/Free_Energy_1e_(Snee)/10:_The_Kinetic_Theory_of_Gas/10.05:_Appendix), /content/body/div[2]/p[4]/span[4], line 1, column 1
Callstack:
at (Bookshelves/Physical_and_Theoretical_Chemistry_Textbook_Maps/Free_Energy_1e_(Snee)/10:_The_Kinetic_Theory_of_Gas/10.05:_Appendix), /content/body/div[2]/p[4]/span[5], line 1, column 1
where \(v=\sqrt{v^2_x+v^2_y+v^2_z}\). The Jacobian \(\left|\frac{\partial (v_x,v_y,v_z)}{\partial (v,\theta ,\phi )}\right|\) is the absolute values of the determinant of the following matrix:
\[\left|
Callstack:
at (Bookshelves/Physical_and_Theoretical_Chemistry_Textbook_Maps/Free_Energy_1e_(Snee)/10:_The_Kinetic_Theory_of_Gas/10.05:_Appendix), /content/body/div[2]/p[6]/span, line 1, column 1
In our coordinate system the absolute value of the determinant of the matrix is:
\[\left|
Callstack:
at (Bookshelves/Physical_and_Theoretical_Chemistry_Textbook_Maps/Free_Energy_1e_(Snee)/10:_The_Kinetic_Theory_of_Gas/10.05:_Appendix), /content/body/div[2]/p[8]/span[1], line 1, column 1
Callstack:
at (Bookshelves/Physical_and_Theoretical_Chemistry_Textbook_Maps/Free_Energy_1e_(Snee)/10:_The_Kinetic_Theory_of_Gas/10.05:_Appendix), /content/body/div[2]/p[8]/span[2], line 1, column 1
Callstack:
at (Bookshelves/Physical_and_Theoretical_Chemistry_Textbook_Maps/Free_Energy_1e_(Snee)/10:_The_Kinetic_Theory_of_Gas/10.05:_Appendix), /content/body/div[2]/p[8]/span[3], line 1, column 1
Callstack:
at (Bookshelves/Physical_and_Theoretical_Chemistry_Textbook_Maps/Free_Energy_1e_(Snee)/10:_The_Kinetic_Theory_of_Gas/10.05:_Appendix), /content/body/div[2]/p[8]/span[4], line 1, column 1
Callstack:
at (Bookshelves/Physical_and_Theoretical_Chemistry_Textbook_Maps/Free_Energy_1e_(Snee)/10:_The_Kinetic_Theory_of_Gas/10.05:_Appendix), /content/body/div[2]/p[8]/span[5], line 1, column 1
Callstack:
at (Bookshelves/Physical_and_Theoretical_Chemistry_Textbook_Maps/Free_Energy_1e_(Snee)/10:_The_Kinetic_Theory_of_Gas/10.05:_Appendix), /content/body/div[2]/p[8]/span[6], line 1, column 1
Callstack:
at (Bookshelves/Physical_and_Theoretical_Chemistry_Textbook_Maps/Free_Energy_1e_(Snee)/10:_The_Kinetic_Theory_of_Gas/10.05:_Appendix), /content/body/div[2]/p[8]/span[7], line 1, column 1
Callstack:
at (Bookshelves/Physical_and_Theoretical_Chemistry_Textbook_Maps/Free_Energy_1e_(Snee)/10:_The_Kinetic_Theory_of_Gas/10.05:_Appendix), /content/body/div[2]/p[8]/span[8], line 1, column 1
Callstack:
at (Bookshelves/Physical_and_Theoretical_Chemistry_Textbook_Maps/Free_Energy_1e_(Snee)/10:_The_Kinetic_Theory_of_Gas/10.05:_Appendix), /content/body/div[2]/p[8]/span[9], line 1, column 1
Callstack:
at (Bookshelves/Physical_and_Theoretical_Chemistry_Textbook_Maps/Free_Energy_1e_(Snee)/10:_The_Kinetic_Theory_of_Gas/10.05:_Appendix), /content/body/div[2]/p[8]/span[10], line 1, column 1
Callstack:
at (Bookshelves/Physical_and_Theoretical_Chemistry_Textbook_Maps/Free_Energy_1e_(Snee)/10:_The_Kinetic_Theory_of_Gas/10.05:_Appendix), /content/body/div[2]/p[8]/span[11], line 1, column 1
Callstack:
at (Bookshelves/Physical_and_Theoretical_Chemistry_Textbook_Maps/Free_Energy_1e_(Snee)/10:_The_Kinetic_Theory_of_Gas/10.05:_Appendix), /content/body/div[2]/p[8]/span[12], line 1, column 1
Callstack:
at (Bookshelves/Physical_and_Theoretical_Chemistry_Textbook_Maps/Free_Energy_1e_(Snee)/10:_The_Kinetic_Theory_of_Gas/10.05:_Appendix), /content/body/div[2]/p[8]/span[13], line 1, column 1
Callstack:
at (Bookshelves/Physical_and_Theoretical_Chemistry_Textbook_Maps/Free_Energy_1e_(Snee)/10:_The_Kinetic_Theory_of_Gas/10.05:_Appendix), /content/body/div[2]/p[8]/span[14], line 1, column 1
Callstack:
at (Bookshelves/Physical_and_Theoretical_Chemistry_Textbook_Maps/Free_Energy_1e_(Snee)/10:_The_Kinetic_Theory_of_Gas/10.05:_Appendix), /content/body/div[2]/p[8]/span[15], line 1, column 1
\[=\left|-v^2(phi )(theta )-v^2
Callstack:
at (Bookshelves/Physical_and_Theoretical_Chemistry_Textbook_Maps/Free_Energy_1e_(Snee)/10:_The_Kinetic_Theory_of_Gas/10.05:_Appendix), /content/body/div[2]/p[10]/span[1], line 1, column 1
Callstack:
at (Bookshelves/Physical_and_Theoretical_Chemistry_Textbook_Maps/Free_Energy_1e_(Snee)/10:_The_Kinetic_Theory_of_Gas/10.05:_Appendix), /content/body/div[2]/p[10]/span[2], line 1, column 1
Callstack:
at (Bookshelves/Physical_and_Theoretical_Chemistry_Textbook_Maps/Free_Energy_1e_(Snee)/10:_The_Kinetic_Theory_of_Gas/10.05:_Appendix), /content/body/div[2]/p[10]/span[3], line 1, column 1
Callstack:
at (Bookshelves/Physical_and_Theoretical_Chemistry_Textbook_Maps/Free_Energy_1e_(Snee)/10:_The_Kinetic_Theory_of_Gas/10.05:_Appendix), /content/body/div[2]/p[10]/span[4], line 1, column 1
Callstack:
at (Bookshelves/Physical_and_Theoretical_Chemistry_Textbook_Maps/Free_Energy_1e_(Snee)/10:_The_Kinetic_Theory_of_Gas/10.05:_Appendix), /content/body/div[2]/p[10]/span[5], line 1, column 1
Callstack:
at (Bookshelves/Physical_and_Theoretical_Chemistry_Textbook_Maps/Free_Energy_1e_(Snee)/10:_The_Kinetic_Theory_of_Gas/10.05:_Appendix), /content/body/div[2]/p[10]/span[6], line 1, column 1
Since we take the absolute value of this result (the negative sign goes away), the final answer is: \(\partial v_x\cdot \partial v_y\cdot \partial v_z=v^2\cdot Callstack:
at (Bookshelves/Physical_and_Theoretical_Chemistry_Textbook_Maps/Free_Energy_1e_(Snee)/10:_The_Kinetic_Theory_of_Gas/10.05:_Appendix), /content/body/div[2]/p[11]/span/span, line 1, column 1
When we apply the Jacobian to the Maxwell-Boltzmann formula we see that (bold emphasis added):
\[{\left(\frac{m}{2\cdot \pi \cdot k_B\cdot T}\right)}^{\frac{3}{2}}\cdot e^{\frac{-m\cdot v^2}{2\cdot k_B\cdot T}}\cdot \partial v_x\cdot \partial v_y\cdot \partial v_z={\left(\frac{m}{2\cdot \pi \cdot k_B\cdot T}\right)}^{\frac{3}{2}}\cdot e^{\frac{-m\cdot v^2}{2\cdot k_B\cdot T}}\cdot v^2\cdot
Callstack:
at (Bookshelves/Physical_and_Theoretical_Chemistry_Textbook_Maps/Free_Energy_1e_(Snee)/10:_The_Kinetic_Theory_of_Gas/10.05:_Appendix), /content/body/div[2]/p[13]/span, line 1, column 1
Now we can integrate out the angles:
\[{\left(\frac{m}{2\cdot \pi \cdot k_B\cdot T}\right)}^{\frac{3}{2}}\cdot e^{\frac{-m\cdot v^2}{2\cdot k_B\cdot T}}\cdot v^2\cdot
Callstack:
at (Bookshelves/Physical_and_Theoretical_Chemistry_Textbook_Maps/Free_Energy_1e_(Snee)/10:_The_Kinetic_Theory_of_Gas/10.05:_Appendix), /content/body/div[2]/p[15]/span[1], line 1, column 1
Callstack:
at (Bookshelves/Physical_and_Theoretical_Chemistry_Textbook_Maps/Free_Energy_1e_(Snee)/10:_The_Kinetic_Theory_of_Gas/10.05:_Appendix), /content/body/div[2]/p[15]/span[2], line 1, column 1
which leaves us with just a constant:
\[\int^{\pi }_0{}
Callstack:
at (Bookshelves/Physical_and_Theoretical_Chemistry_Textbook_Maps/Free_Energy_1e_(Snee)/10:_The_Kinetic_Theory_of_Gas/10.05:_Appendix), /content/body/div[2]/p[17]/span[1], line 1, column 1
Callstack:
at (Bookshelves/Physical_and_Theoretical_Chemistry_Textbook_Maps/Free_Energy_1e_(Snee)/10:_The_Kinetic_Theory_of_Gas/10.05:_Appendix), /content/body/div[2]/p[17]/span[2], line 1, column 1
leaving us with:
\[4\pi \cdot v^2\cdot {\left(\frac{m}{2\cdot \pi \cdot k_B\cdot T}\right)}^{\frac{3}{2}}\cdot e^{\frac{-m\cdot v^2}{2\cdot k_B\cdot T}}\cdot \partial v \nonumber \]
This is the velocity form of the Maxwell-Boltzmann equation.
A.2.
\(\partial v_a\cdot \partial v_b\to \partial G\cdot \partial V_{rel}\): The following Jacobian was used in the calculation of relative velocity:
\[\partial v_a\cdot \partial v_b=\left|\frac{\partial (v_a,v_b)}{\partial (G,V_{rel})}\right|\cdot \partial G\cdot \partial V_{rel} \nonumber \]
The determinant is:
\[\left|\frac{\partial (v_a,v_b)}{\partial (G,V_{rel})}\right|=\left|det\left[\frac{\partial v_a}{\partial V_{rel}}frac{\partial v_a}{\partial G}frac{\partial v_b}{\partial V_{rel}}frac{\partial v_b}{\partial G}right]\right| \nonumber \]
Given that \(v_a=G+\frac{m_b}{m_a+m_b}V_{rel}\) and \(v_b=G-\frac{m_a}{m_a+m_b}V_{rel}\), we can fill out the matrix:
\[\left|det\left[\frac{m_b}{m_a+m_b}\ 1\ -\frac{m_a}{m_a+m_b}\ 1right]\right|=\frac{m_b}{m_a+m_b}+\frac{m_a}{m_a+m_b}=\frac{m_a+m_b}{m_a+m_b}=1 \nonumber \]
Done!