The expression \( 5\sqrt{3} \) can be rewritten using exponent rules. The square root can be expressed as an exponent of \( \frac{1}{2} \). Therefore, we can express the square root as follows:
\[ \sqrt{3} = 3^{\frac{1}{2}} \]
So, \( 5\sqrt{3} \) can be rewritten as:
\[ 5 \cdot 3^{\frac{1}{2}} \]
The rational exponent for the square root of 3 in this expression is \( \frac{1}{2} \). Therefore, the answer is:
\[ \frac{1}{2} \]