New experimental tests of existing interpretations of electronic transitions of ethylene

Abstract

The absorption spectra of the gases ethylene-do, d I' I, I-d" cis-d" trans-d" d 3 , and d 4 have been photographed using the first order of a 21-ft vacuum spectrograph. Analyses of both the Rydberg system at 1750 A and the 7r*-7r system between 1500 and 2100 A have been extended. Band contour analysis has confirmed the assignment of the Rydberg system as I B 3" _IA g' The resulting rotational constants of the 4 2 level of the excited state of C,D 4 lead to an inertial defect indicative of a non planar molecule. Assuming point group D" we have combined the constants with Franck-Condon calculations in a complete structure determination for the 4' level of the Rydberg state: rcc=1.41 A, r cH =1.08 A, ~ HCH=124.4° and an azimuthal angle of 31'. Linewidths in the successful simulation of the C,D 4 0--0 band indicate a lifetime greater than 10-13 sec for molecules in the zero level of the Rydberg state. For the 7r*-7r system, all observed bands for all molecules studied have been assigned. Most striking is the relative inactivity of the C-C stretching vibration; except in C,D 4 , only the torsional mode is active. It is concluded that r cc for the 7r*-7r state is not very different than it is for the Rydberg state. Finally, the extrapolation to the (unobserved) origin of the 7r*-7r system is revised to give 5.5 eV (2285 A).

The first and second derivative matrices in the random phase approximation scheme by using the Lagrangian technique

“…Table II shows the results of ethylene molecule on the first excited state. Our RPA results are quite similar to the CIS calculation, where the geometry of the first excited state is plane structure, while the experimental dihedral angle is 37.0 [26]. The vertical excitation energies of RPA and CIS calculations are 7.23 and 7.24 eV, respectively, which are similar to the experimental results of 7.11 eV [27].…”

Coupled cluster calculations of the vertical excitation energies of tetracyanoethylene

“…In this way, we estimate the value of the 0-0 transition to be 5.42 eV, in very good agreement with the experimental value of 5.50 eV extrapolated from the experimental spectra by Foo and Innes. 43 The 0-0 transition has also been computed by Mebel et al, 14 at D 2 geometry who proposed a value of 5.45 eV combining CASSCF͑2/11͒ and MRCI calculations. However, recently Ben-Nun and Martínez studied the conical intersections between electronic states of ethylene and found a pyramidalized structure for the V state from both CASSCF͑2/6͒ and MRCI calculations 44 and ab initio multielectronic state molecular dynamics.…”

Role of Rydberg States in the Photochemical Dynamics of Ethylene

“…27 The exponent of this orbital was set to 0.0208 (in atomic units), which was determined by fitting the energy of the π-3s Rydberg [Ryd(3s) in Mulliken notation] state at the FranckÀCondon (FC) and Ryd(3s)/ππ* intersection geometries to previous computational and experimental results. 18,20,24,43,44 Details of the fitting procedure are provided in Supporting Information. The CASSCF active space consisted of three orbitals (π, π*, and 3s) with two electrons.…”