Ultraviolet-ultraviolet hole burning spectroscopy in a quadrupole ion trap: dibenzo[18]crown-6 complexes with alkali metal cations.

Conformation selective: A new technique of ultraviolet-ultraviolet hole burning spectroscopy that can be applied to ions stored in a quadrupole ion trap (QIT) is developed and used to obtain the conformation-selective electronic spectra of dibenzo[18]crown-6 complexes with alkali metal cations (M(+), see picture; F(+) = fragment).