Electronic sum-frequency generation (ESFG) spectroscopy: theoretical formulation of resonances with symmetry-allowed and symmetry-forbidden electronic excited states

ABSTRACT

Sum-frequency generation spectroscopy is a powerful tool for analysing molecular species and orientation configurations on a surface or an interface. In addition to conventional vibrational resonant techniques, the electronic resonant (electronic sum-frequency generation [ESFG]) ones have been developed recently. We have established the theoretical formulation of ESFG spectroscopy based on the susceptibility approach, considering resonances with both symmetry-allowed and symmetry-forbidden electronic excited states; derivatives of transition dipole moments and vibronic couplings beyond the Condon approximation were included. With the aid of density functional theory computations, simulated ESFG spectra in resonances with both types of excited states of acetone are demonstrated.

KEYWORDS:

• Sum-frequency generation
• electronic excited state
• symmetry-forbidden transition
• vibronic coupling
• acetone

Acknowledgments

The authors are grateful to the National Center for High-performance Computing (NCHC Taiwan) for computer time and facilities. This research is supported by a grant from Ministry of Science and Technology [grant number MOST 105-2119-M-002-033-MY2] of Taiwan, ROC.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

Ministry of Science and Technology, Taiwan [grant number MOST 105-2119-M-002-033-MY2].