Dipole moment functions of iodine E0g –A1uand E0g –B  1utransitions

The ion-pair states of molecular iodine provide a unique system for studying the efficiency, selectivity, and mechanisms of collision-induced non-adiabatic transitions. Non-adiabatic transitions between the first-tier ion-pair states in collisions with molecular partners and rare gases are analyzed and discussed. The qualitative features of the rate constants and product state distributions under single collision conditions are summarized and interpreted in terms of appropriate theoretical approaches. Two mechanisms for the non-adiabatic transitions are clearly identified. The first, operative for collisions involving molecular partners possessing permanent or transition electrostatic moments, is highly selective. It connects the initially prepared level in the E 0 þ g electronic state with the near-resonant vibronic level of the D 0 þ u state with a minimum change of the total angular momentum. In an extreme quasi-resonant case when the gap between initial and final rovibronic level is less than 1 cm À1 , this mechanism has a giant cross section, 40 times that of a gas kinetic collision. An electrostatic model, which includes the coupling of the giant E-D transition dipole moment with a moment of the colliding partner and the semiclassical Born approximation, provides a plausible interpretation of this mechanism. A second mechanism is shown to govern collisions with rare gas atoms. It results in population of several ion-pair states and broad distributions over rovibronic levels. This mechanism is successfully interpreted by quantum scattering calculations based on the diatomics-in-molecule diabatic potential energy surfaces and coupling matrix elements. The calculations provide good agreement with experimental measurements and reveal different mechanisms for the population of different electronic states. Unexplained features of the non-adiabatic dynamics and directions of future work are outlined.

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“…As in the case of v E ¼ 0 excitation, CINAT was observed only to D 0 þ u state. 65,67,76 As shown in Fig. 2, the total rate constant for the E !…”

Section: Electronic Structure Of Ip Statesmentioning

confidence: 87%

“…The experimental techniques used at Swarthmore and St. Petersburg to investigate the CINAT dynamics of I 2 (E) are similar (see details in refs. [65][66][67][68][69][70][71][72]76,77). Single rovibrational levels of the E 0 þ g state were populated through an OODR excitation scheme:…”

Section: Experimental and Theoretical Background 21 Experimental Tecmentioning

confidence: 99%

Collision-induced non-adiabatic transitions between the ion-pair states of molecular iodine: A challenge for experiment and theory

Tscherbul

Buchachenko

Akopyan

et al. 2004

Phys. Chem. Chem. Phys.

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“…The calculated spectra had an estimated wavelength accuracy of ±0.01 Å and agreed well with the literature data. 25 The spectroscopic constants and/or potential curves from the following sources: X state, 26 B, 27 D, 28 a 0 + g , 24,28 A1 u , B 1 u , 29 were used for the experimental data analysis. Dipole moment functions for the D-X and E-B transitions were taken from Ref.…”

Section: Methodsmentioning

confidence: 99%

“…Nevertheless, one would believe that its intensity is much lower than that of the one-electron high frequency D → X transition. The D → X spectra are overlapped with the E-A and E-B , 29 and we simulated the D → X spectra to determine their total intensity.…”

Section: Methodsmentioning

confidence: 99%

Non-adiabatic transitions from I2(${E} {\rm 0}_{g}^{+} $Eg+ and ${D}0_{u}^{+} $Du+) states induced by collisions with M = I2(${X}0_{g}^ + $Xg+) and H2O

Akopyan

Baturo

Lukashov

et al. 2012

The Journal of Chemical Physics

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The stepwise two-step two-color and three-step three-color laser excitation schemes are used for selective population of rovibronic levels of the first-tier ion-pair E0(g)(+) and D0(u)(+) states of molecular iodine and studies of non-adiabatic transitions to the D and E states induced by collisions with M = I(2)(X) and H(2)O. Collection and analysis of the luminescence after excitation of the v(E) = 8, 13 and v(D) = 13, 18 vibronic levels of the E and D states in the pure iodine vapor and the gas-phase mixtures with H(2)O provide rate constants for the non-adiabatic transitions to the D and E state induced by collisions with these molecules. Vibrational distributions for the [formula: see text] collision-induced non-adiabatic transitions (CINATs) are obtained. Rather strong λ(lum)(max) ≈ 3400 Å luminescence band is observed in the I(2) + H(2)O mixtures, whereas its intensity is ~100 times less in pure iodine vapor. Radiative lifetimes and quenching rate constants of the I(2)(E,v(E) = 8, 13 and D,v(D) = 13, 18) vibronic state are also determined. Rate constants of the [formula: see text], v(E) = 8-54, CINATs are measured again and compared with those obtained earlier. New data confirm resonance characters of the CINATs found in our laboratory about 10 years ago. Possible reasons of differences between rate constant values obtained in this and earlier works are discussed. It is shown, in particular, that differences in rate constants of non-resonant CINATs are due to admixture of water vapor in iodine.

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“…C1 u (aa) emission. Subsequently, Akopyan et al [19] showed by simulation that the E0 þ g ð 3 P 2 Þðv ¼ 9Þ ! C1 u (aa) emission has a red extremum at 350 nm.…”

Section: General Implications For Other Collisional Energy Transfer Ementioning

confidence: 99%

The influence of amplified spontaneous emission in collisional energy transfer studies exemplified by to transfer in I2

2008

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Dipole moment functions of iodine E0_g–A1_uand E0_g–B 1_utransitions

Cited by 10 publications

References 26 publications

Collision-induced non-adiabatic transitions between the ion-pair states of molecular iodine: A challenge for experiment and theory

Collision-induced non-adiabatic transitions between the ion-pair states of molecular iodine: A challenge for experiment and theory

Non-adiabatic transitions from I2(${E} {\rm 0}_{g}^{+} $Eg+ and ${D}0_{u}^{+} $Du+) states induced by collisions with M = I2(${X}0_{g}^ + $Xg+) and H2O

The influence of amplified spontaneous emission in collisional energy transfer studies exemplified by to transfer in I2

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