an> <span class="n">PSI_ROT_exp</span>
  <span class="c">!! Argument of exponential comprising 2D Gaussian distribution </span>

  <span class="n">PSI_ROT_exp</span><span class="o">=</span><span class="p">(</span><span class="n">R</span><span class="o">-</span><span class="n">R0</span><span class="p">)</span><span class="o">**</span><span class="mi">2</span><span class="o">*</span><span class="p">((</span><span class="nb">cos</span><span class="p">(</span><span class="n">theta</span><span class="p">))</span