Two-photon absorption of soft X-ray free electron laser radiation by graphite near the carbon K-absorption edge

Lam RK; Raj SL; Pascal TA; Pemmaraju CD; Foglia L; Simoncig A; Fabris N; Miotti P; Hull CJ; Rizzuto AM; Smith JW; Mincigrucci R; Masciovecchio C; Gessini A; De Ninno G; Diviacco B; Roussel E; Spampinati S; Penco G; Di Mitri S; Trovo M; Danailov MB; Christensen ST; Sokaras D; Wengk TC; Coreno M; Poletto L; Drisdell WS; Prendergast D; Giannessi L; Principi E; Nordlund D; Saykally RJ; Schwartz CP

Chemical Physics Letters, Vol.703, 112-116, 2018

DOI10.1016/j.cplett.2018.05.021 Export Citation

Two-photon absorption of soft X-ray free electron laser radiation by graphite near the carbon K-absorption edge

Lam RK, Raj SL, Pascal TA, Pemmaraju CD, Foglia L, Simoncig A, Fabris N, Miotti P, Hull CJ, Rizzuto AM, Smith JW, Mincigrucci R, Masciovecchio C, Gessini A, De Ninno G, Diviacco B, Roussel E, Spampinati S, Penco G, Di Mitri S, Trovo M, Danailov MB, Christensen ST, Sokaras D, Wengk TC, Coreno M, Poletto L, Drisdell WS, Prendergast D, Giannessi L, Principi E, Nordlund D, Saykally RJ, Schwartz CP

We have examined the transmission of soft X-ray pulses from the FERMI free electron laser through carbon films of varying thickness, quantifying nonlinear effects of pulses above and below the carbon K-edge. At typical of soft X-ray free electron laser intensities, pulses exhibit linear absorption at photon energies above and below the K-edge, similar to 308 and similar to 260 eV, respectively; whereas two-photon absorption becomes significant slightly below the K-edge, similar to 284.2 eV. The measured two-photon absorption cross section at 284.18 eV (similar to 6 x 10(-48) cm(4) s) is 7 orders of magnitude above what is expected from a simple theory based on hydrogen-like atoms - a result of resonance effects. Published by Elsevier B.V.