The vibrational degrees of freedom of the only photophysical intermediate formed during the photoreaction of an artificial rhodopsin (Rh) containing a retinal with a seven-membered ring blocking 11-cis isomerization (Rh7.10) is measured via picosecond time-resolved coherent anti-Stokes Raman spectroscopy (PTR/CARS), PTR/CARS spectra are recorded with time delays ranging from 0 (8-ps cross correlation time) to 50 ps following the 3-ps, 500-nm excitation of Rh7.10. For time delays between 0 and 15 ps, an intermediate (P7.10) with a vibrational structure distinct from that of the ground electronic state Rh7.10 is observed. Although the formation time of P7.10 cannot be resolved from these PTR/CARS data, it is estimated to be similar to 1 ps (i.e., slower than the 200-fs process proposed for native Rh), P7.10 completely reforms Rh7.10 with a decay time estimated to be similar to 5-6 ps from the increasing intensities (via amplitudes from third-order, nonlinear susceptibility (chi((3))) analysis) in three major PTR/CARS features (at 955, 1235, and 1551 cm(-1)). The structural changes occurring as P7.10 is formed can be derived from vibrational mode assignments in the PTR/CARS spectra such as the 955-cm(-1) band assigned as the HC11=C12H hydrogen-out-of-plane (HOOP) mode (shifts to 946 cm(-1), increases intensity, and broadens its width in P7.10) and the 1551-cm(-1) band assigned as the C=C stretching mode (shifts to 1546 cm(-1) in P7.10). These PTR/CARS data show that incorporation of an 11-ene, seven-membered ring into the retinal chromophore permits some flexibility for torsional motion around the C-11=C-12 bond and within the seven-membered ring, but does not allow considerable out-of-plane motion near the Schiff base or the beta-ionone ring. The chi((3)) analysis of these PTR/CARS data demonstrates that a series of structurally-distinct retinals having slightly different C-11=C-12 torsional, out-of-plane motion appear (collectively P7.10). The amplitudes and shifts in frequency of the PTR/CARS vibrational features change on a time scale comparable to that of vibrational relaxation in native Rh. The structural variations observed within P7.10 an located at/near the C-11/C-12 bond (reactive in native Rh-RT, but nonreactive in R7.10) and the degree of pi-electron energy delocalization throughout the retinal changes. This latter phenomenon is reflected in the different electronic phase factor (Theta) found in the chi((3)) analysis of the PTR/CARS data. The relationship(s) of the P7.10 structure to that of the C-11=C-12 reaction coordinates in native Rh is discussed.