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Understanding laser desorption with circularly polarized light
Author(s) -
Ristow Florian,
Scheffel Jakob,
Xu Xuqiang,
Fehn Natalie,
Oberhofer Katrin E.,
Riemensberger Johann,
Mortaheb Farinaz,
Kienberger Reinhard,
Heiz Ulrich,
Kartouzian Aras,
Iglev Hristo
Publication year - 2020
Publication title -
chirality
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.43
H-Index - 77
eISSN - 1520-636X
pISSN - 0899-0042
DOI - 10.1002/chir.23279
Subject(s) - crystallization , chemistry , second harmonic generation , desorption , circular dichroism , circular polarization , analytical chemistry (journal) , optical microscope , laser , microscopy , scanning electron microscope , optics , crystallography , adsorption , organic chemistry , physics , microstrip
We present aspects of emerging optical activity in thin racemic 1,1′‐Bi‐2‐naphthol films upon irradiation with circularly polarized light and subsequent resonant two‐photon absorption in the sample. Thorough analysis of the sample morphology is conducted by means of (polarization‐resolved) optical microscopy and scanning electron microscopy (SEM). The influence of crystallization on the nonlinear probing technique (second harmonic generation circular dichroism [SHG‐CD]) is investigated. Optical activity and crystallization are brought together by a systematic investigation in different crystallization regimes. We find crystallization to be responsible for two counter‐acting effects, which arise for different states of crystallization. Measuring crystallized samples offers the best signal‐to‐noise ratio, but it limits generation of optical activity due to self‐assembly effects. For suppression of crystallization on the other hand, there is a clear indication that enantiomeric selective desorption is responsible for the generation of optical activity in the sample. We reach the current resolution limit of probing with SHG‐CD, as we suppress the crystallization in the racemic sample during desorption. In addition, intensity‐dependent measurements on the induced optical activity reveal an onset threshold (≈0.7 TW cm −2 ), above which higher order nonlinear processes impair the generation of optical activity by desorption with CPL.