The short and highly coherent pulses emitted by modern free electron lasers offer exciting new scientific opportunities. Recently, we traveled to FERMI in Italy and leveraged the capabilities of their free electron laser to develop the technique of soft x-ray second harmonic generation spectroscopy.
In this critical new technique, we seek to combine the element specificity of x-ray spectroscopies with the unique capabilities of second order nonlinear spectroscopy to selectively probe interfaces. Our initial experiments were able to confirm that the signal measured was indeed interface specific and displayed resonant enhancement that is characteristic of SHG processes.
Moving forward, we plan to explore the technique's ability to probe buried interfaces and explore the possibility of combining spectroscopy and lens-less imaging.
Lam, R. K., Raj, S. L., Pascal, T. A., Pemmaraju, C. D., Foglia, L., Simoncig, A., Fabris, N., Miotti, P., Hull, C. J., Rizzuto, A. M., Smith, J. W., Mincigrucci, R., Masciovecchio, C., Gessini, A., Allaria, E., De Ninno, G., Diviacco, B., Roussel, E., Spampinati, S., Penco, G., Di Mitri, S., Trovò, M., Danailov, M., Christensen, S. T., Sokaras, D., Weng, T.-C., Coreno, M., Poletto, L., Drisdell, W. S., Prendergast, D., Giannessi, L., Principi, E., Nordlund, D., Saykally, R. J., Schwartz, C. P. "Soft X-Ray Second Harmonic Generation as an Interfacial Probe " Phys. Rev. Lett., 120, 023901 (2018) (SI). (Viewpoint).
Lam, R. K., Raj, S. L., Pascal, T. A., Pemmaraju, C. D.,Foglia, L., Simoncig, A., Fabris, N., Miotti, P., Hull, C. J., Rizzuto, A. M., Smith, J. W., Mincigrucci, R., Masciovecchio, C., Gessini, A., De Ninno, G., Diviacco, B., Roussel, E., Spampinati, S., Penco, G., Di Mitri, S., Trovò, M., Danailov, M. B., Christensen, S. T., Sokaras, D., Weng, T-C., Coreno, M., Poletto, L., Drisdell, W. S., Prendergast, D., Giannessi, L., Principi, E., Nordlund, D., Saykally, R. J., Schwartz, C. P. "Two-photon absorption of soft X-ray free electron laser radiation by graphite near the carbon K-absorption edge" Chem. Phys. Lett., 703, pp 112-116 (2018).