at ELISA, as well as by direct detection in a separate laboratory [35], results from
prompt vibrational autodetachment (VAD) out of the first excited state of the GFP
chromophore anion [36]. VAD is enabled through a non-adiabatic energy-sharing
mechanism between the electronic and nuclear dynamics.
As discussed, at ELISA we are able to detect the prompt neutral chromophores
from PD as well as neutral fragments created in statistical processes from the hot S 0
electronic ground state after IC. The timing information of the present experiment is
unique and is used to separate the PD versus IC decay modes. The ratio between the
two channels is related to the preference of the molecular chromophore to respond
by transferring energy into the electronic degrees of freedom or into the nuclear
motion.
5.2.3 Signal Detection
It is evident from Fig. 5.8 that the SED was recording a very significant prompt
signal at 485 nm (close to the S 1 action absorption maximum previously registered
at 479 nm (2.59 eV) [20]). A delayed signal is seen in both detectors at 485 nm, but
not on any of the detectors at 415 nm, for example, where only the prompt
Direct electron
detachment
{neutral + e - }
Indirect electron
detachment
{neutral + e - }
V q =0
V q =1
q
0
1
S 0
S 1
anion
anion
E e
neutral
PD
V q =0
V q =1
q
0
1
IC
S 0
Hot S 0
S 1
anion
anion
Fragmentation
{neutral + anion}
IC
Thermionic
emission
{neutral + e - }
SF
Tem
E e
Fig. 5.7 Photoresponse after excitation in the S 1 spectral region. Left: photodetachment (PD) via
resonant excitation to S 1 as well as non-resonant detachment directly into the continuum. Right:
internal conversion (IC) into a vibrationally hot anion in the electronic ground state S 0 . From the
hot S 0 state statistical fragmentation (SF) or thermionic electron emission (Tem) may occur. V q
denotes a vibrational mode
5 Photo-initiated Dynamics and Spectroscopy of the Deprotonated Green. . .
77