•Please use ChatGPT to explore a thematic series of questions within the scope of computational chemistry and follow up with further inquiries about any unfamiliar terms  ( except homework )

•Calculate the first 13 excited states of the Hydrogen atom by using the CIS theoretical method with appropriate basis sets ( need to include diffuse functions or other elements ) then compare with the experimental values.

• From the figure, we can be seen that the method CIS with the D(+)-aug-cc-pVQZ basis set have the lowest absolute error,so D(+)-aug-cc-pVQZ is the best basis set .

•Calculate the first 5 singlet excited states of Helium by using the CIS、CIS(D) theoretical method with appropriate basis sets then compare with the experimental values.

• From the figure, we can be seen that the method CIS with the (++)d-aug-cc-pVQZ basis set have the lowest absolute error,so (++)d-aug-cc-pVQZ is the best basis set .
• Reference:NIST Atomic Spectra Database