Para-Propylphenol Quantum Theoretical Calculation And Resonance Multi-Photon Ionization Spectroscopy

The molecular structure of p-propylphenol is similar to that of tyrosine. The research about p-propylphenol structure and energy is helpful to understand optical and biochemical properties of Amino acids tyrosine. In this paper, quantum chemistry theory calculations with different sizes of basis function sets are performed for p-propylphenol structures, energy, ionization energy, potential energy surface and vibration frequency for both neutral ground state, ion ground state and electrically excited state. We determined three rotational isomers of propylphenol by calculation, and simulated the vibration spectrum. The results show that the diffuse functions have a very significant effect both on simulation spectra and on the transition intensity. The results with more diffuse functions are significantly different from those with a single and without diffuse functions. The effect of the polarization function on the vibrational frequencies and transition strengths is not obvious. Compare to the experimental results, we found that the larger the basis set, the closer calculated frequency and the spectrum intensity to the experimental results.Using the large basis set of 6-311++G(d,p), we successfully calculated the energies and vibrational frequencies of p-propylphenol excited states. Compare to literature results based on small basis set of 6-31G, we give a more accurate and comprehensive theoretical data. On the basis of careful analysis of the experimental spectra, we gives more reliable vibration mode identifications.