A one-dimensional anharmonic oscillator is treated by perturbation theory. The harmonic oscillator is used as the unperturbed system and the perturbation is $\frac{1}{6} \gamma \mathrm{x}^{3}$ ( $\gamma$ is a constant). Using only the first order correction, the total ground state energy of the anharmonic oscillator is Note: For aone-dimensional harmonic oscillator $\psi_{0}(\mathrm{x})=\left(\frac{\alpha}{\pi}\right)^{1 / 4} \mathrm{e}^{-\alpha \mathrm{x}^{2}} ; \alpha=\left(\frac{\mathrm{k} \mu}{\mathrm{h}^{2}}\right)^{1.2}$