Spin-Orbit Interaction in Aromatic Molecules

The high-resolution single-photon pulsed-field-ionization zero-kinetic-energy photoelectron spectra of the \documentclass[12pt]{minimal}\begin{document}$\tilde{\rm {X}}^+$\end{document}X̃+ 2\documentclass[12pt]{minimal}\begin{document}$\rm {E_{3/2}}\leftarrow \tilde{\rm {X}}\, ^1{\rm A}_1$\end{document}E3/2←X̃1A1 transition of CH3I and CD3I have been recorded. The spectral resolution of better than 0.15 cm−1 enabled the observation of the rotational structure. CH3I+ and CD3I+ are subject to a weak \documentclass[12pt]{minimal}\begin{document}$\rm {E}\otimes \rm {e}$\end{document}E⊗e Jahn–Teller effect and strong spin–orbit coupling. The treatment of the rovibronic structure of the photoelectron spectra in the corresponding spin double group, \documentclass[12pt]{minimal}\begin{document}$\rm {C_{3v}^2(M)}$\end{document}C3v2(M), including the effects of the spin–orbit interaction and the vibrational angular momentum, allowed the reproduction of the experimentally observed transitions with spectroscopic accuracy. The relevant spin–orbit and linear Jahn–Teller coupling parameters of the \documentclass[12pt]{minimal}\begin{document}$\tilde{\rm {X}}^+$\end{document}X̃+ ground state were derived from the analysis of the spectra of the two isotopomers, and improved values were obtained for the adiabatic ionization energies [\documentclass[12pt]{minimal}\begin{document}${E_{\rm {I}}(\rm {CH}_3\rm {I})}/hc =76931.35(20)$\end{document}EI( CH 3I)/hc=76931.35(20) cm−1 and \documentclass[12pt]{minimal}\begin{document}${E_{\rm {I}}(\rm {CD}_3\rm {I})}/hc=76957.40(20)$\end{document}EI( CD 3I)/hc=76957.40(20) cm−1] and the rotational constants of the cations. Rovibronic photoionization selection rules were derived for transitions connecting neutral states following Hund's-case-(b)-type angular momentum coupling and ionic states following Hund's-case-(a)-type coupling. The selection rules, expressed in terms of the angular momentum projection quantum number P, account for all observed transitions and provide an explanation for the nonobservation of several rotational sub-bands in the mass-analyzed threshold-ionization spectra of \documentclass[12pt]{minimal}\begin{document}$\rm {CH}_3\rm {I}$\end{document} CH 3I and \documentclass[12pt]{minimal}\begin{document}$\rm {CD}_3\rm {I}$\end{document} CD 3I reported recently by Lee et al. [J. Chem. Phys. 128, 044310 (2008)].

Section: A Vibronic and Spin-orbit Coupling In The 2 E Electronic Grmentioning

confidence: 99%

Photoelectron spectroscopic study of the E⊗e Jahn–Teller effect in the presence of a tunable spin–orbit interaction. I. Photoionization dynamics of methyl iodide and rotational fine structure of CH3I+ and CD3I+

Grütter

Michaud

Merkt

2011

“…This represent's the usual case for phosphorescence in triplet states. 16 It might be noted that this is the analogue of the optical case discussed in connection with Fig. 1(b).…”

Section: P*(t)= Ct 1 P(t) Umentioning

confidence: 99%

“…different symmetry due to spin-orbit coupling. 16 The triplet terms will vamsh when pJ operates on 1' .. ' but the singlet ad-. mixture will, give a nonzero amplitude which we define as (25) From Eqs.…”

Section: P*(t)= Ct 1 P(t) Umentioning

confidence: 99%

See 1 more Smart Citation

Coherence in multilevel systems. I. Coherence in excited states and its application to optically detected magnetic resonance in phosphorescent triplet states

Breiland

Brenner

Harris

1975

A method for monitoring the time development of the coherent components in a multilevel system using an observable which can measure only the relative populations in the levels is presented. Using standard density matrix formulation, expressions are obtained for the conventional and this new ’’probe’’ pulse method. For several of the more common coherence experiments, optically detected magnetic resonance of molecular excited triplet states is used to illustrate the principles. The effect of coherent averaging of relaxation terms in the spin Hamiltonian is discussed and specifically applied to excited triplet states in zero field. Finally, experimental results of coherence measurements are presented along with a detailed description of the apparatus and methods used.

“…The electronic 2 E 1g ground state of benzene ϩ , in D 6h symmetry, has a substantial electronic orbital angular momentum about the sixfold axis, but it has been known for a long time from EPR ͑electron paramagnetic resonance͒ studies 24,25 that spin-orbit coupling is very small. High-resolution optical spectra 26 -28 gave an upper bound of 0.01 cm Ϫ1 for the spinorbit splittings in C 5 H 5 and it is expected that they are of similar small size in benzene ϩ .…”

Section: Introductionmentioning

confidence: 99%

Jahn–Teller effect in van der Waals complexes; Ar–C6H6+ and Ar–C6D6+

Avoird

Lotrich

2004

Please be advised that this information was generated on 2018-05-11 and may be subject to change. The two asymptotically degenerate potential energy surfaces of argon interacting with the X 2 E 1g ground state benzene ϩ cation were calculated ab initio from the interaction energy of the neutral Ar-benzene complex given by Koch et al. ͓J. Chem. Phys. 111, 198 ͑1999͔͒ and the difference of the geometry-dependent ionization energies of the complex and the benzene monomer computed by the outer valence Green's function method. Coinciding minima in the two potential surfaces of the ionic complex occur for Ar on the C 6v symmetry axis of benzene ϩ ͑the z axis͒ at z e ϭ3.506 Å. The binding energy D e of 520 cm Ϫ1 is only 34% larger than the value for the neutral Ar-benzene complex. The higher one of the two surfaces is similar in shape to the neutral Ar-benzene potential, the lower potential is much flatter in the (x,y) bend direction. Nonadiabatic ͑Jahn-Teller͒ coupling was taken into account by transformation of the two adiabatic potentials to a two-by-two matrix of diabatic potentials. This transformation is based on the assumption that the adiabatic states of the Ar-benzene ϩ complex geometrically follow the Ar atom. Ab initio calculations of the nonadiabatic coupling matrix element between the adiabatic states with the two-state-averaged CAS-SCF͑5,6͒ method confirmed the validity of this assumption. The bound vibronic states of both Ar-C 6 H 6 ϩ and Ar-C 6 D 6 ϩ were computed with this two-state diabatic model in a basis of three-dimensional harmonic oscillator functions for the van der Waals modes. The binding energy D 0 ϭ480 cm Ϫ1 of the perdeuterated complex agrees well with the experimental upper bound of 485 cm Ϫ1 . The ground and excited vibronic levels and wave functions were used, with a simple model dipole function, to generate a theoretical far-infrared spectrum. Strong absorption lines were found at 10.1 cm Ϫ1 ͑bend͒ and 47.9 cm Ϫ1 ͑stretch͒ that agree well with measurements. The unusually low bend frequency is related to the flatness of the lower adiabatic potential in the (x,y) direction. The van der Waals bend mode of e 1 symmetry is quadratically Jahn-Teller active and shows a large splitting, with vibronic levels of A 1 , E 2 , and A 2 symmetry at 1.3, 10.1, and 50.2 cm Ϫ1 . The level at 1.3 cm Ϫ1 leads to a strong absorption line as well, which could not be measured because it is too close to the monomer line. The level at 50.2 cm Ϫ1 gives rise to weaker absorption. Several other weak lines in the frequency range of 10 to 60 cm Ϫ1 were found. Jahn-Teller effect in van der