Ultrafast decay dynamics of electronically excited 2-ethylpyrrole

Abstract

The excited-state decay dynamics of 2-ethylpyrrole following UV excitation at a wavelength range of 254.8-218.0 nm is investigated in detail using femtosecond time-resolved photoelectron imaging method. The time-resolved photoelectron spectra at all pump wavelengths are carefully analysed and the following picture is derived: At the longest pump wavelengths (254.8, 248.3 and 246.1 nm), 2-ethylpyrrole is excited to the S1(1πσ*) state having a lifetime of about 50 fs. At 248.3, 246.1 and 237.4 nm, another excited state of Rydberg character is excited. The lifetime of this state is ~570 fs at 237.4 nm and becomes slightly longer at other two pump wavelengths. At the shortest pump wavelengths (230.8 and 218.0 nm), 2-ethylpyrrole is excited to a state which is tentatively assigned to the 1ππ* state, having a lifetime of 88±15 and 55±10 fs for the longer and shorter pump wavelengths, respectively.