Non-adiabatic transitions between first tier ion-pair states of I2 induced by collisions with Ar atoms

Abstract

a b s t r a c tNon-adiabatic transitions from the I 2 (E0 þ g , D0 þ u , b1 g and D 0 2 g ) states to first tier ion-pair (IP) states induced by collisions with Ar atoms have been investigated. The stepwise laser excitation schemes have been used for selective population of close-lying vibronic states:Rate constants of population of the first tier ion-pair states from the optically populated rovibronic states as well as rate constants of depopulation of the states have been determined. Analysis of the mechanism of the transitions has been carried out.We find that the k max lum % 3410 Å luminescence band in the case of optical population of the D and b states cannot be described assuming the collision-induced non-adiabatic transitions only. We conclude that there is an additional radiative channel for population of the states, probably, due to the formation of the ArI 2 (IP) van der Waals complexes.

Hyperfine coupling of the iodine ${\boldsymbol{D}}{0}_{{\boldsymbol{u}}}^{+}$ andβ1gion-pair states

“…To determine ratios of integrated intensities of the D→X and β→A luminescence (see section 3) we measured luminescence spectra in the λ lum ≈2400-4500 Å range at the excitation lines corresponding to a simultaneous population of the D, v D , J D and β, v β , J β rovibronic states. Uncertainties of the total D→X, β→A luminescence intensities depend mainly on those of spectra simulation (see [4,5,[27][28][29] for details).…”

“…A detailed description of experimental apparatus has been given elsewhere (see [4,[27][28][29] and references). Briefly, the Quantel system consisting of two tunable dye TDL90 lasers pumped with a pulsed YG981C Nd:YAG laser has been utilized.…”

“…Such perturbations of the states occur in free (isolated) molecules (intramolecular perturbations) as well as in weakly bound molecular complexes and collisions of molecules with a partner (intermolecular perturbations). Different types of intramolecular perturbations have been studied in numerous experimental and theoretical works since the beginning of the 20th century [1][2][3][4][5][6][7].…”

Energy Transfer in the 2u (1D2) Ion-Pair State of I2 by Inelastic Collisions with Noble Gas Atoms

“…Several studies on the collisional and reaction processes in the ion-pair states of I 2 molecules with noble gas atoms have been conducted. Akopyan et al investigated the collisional process of E 0 g + ( 3 P 2 ) and D 0 u + ( 3 P 2 ) states in the first tier and the f 0 g + ( 3 P 0 ) state in the second tier with He, Ar, Kr, and Xe. − Similar to the self-quenching process, transitions between the ion-pair states correlated to the same dissociation limit are observed primarily. However, the behavior for the first tier was different from that of the second tier.…”

Cross-sections of bound-free ${\rm I}_2 ( 0_g^ + , \mathop 1\nolimits_g (aa, ab)\buildrel{{\scriptstyle hv_{f}}}\over{\longleftarrow \!\!\!\! - \!\!\! - \!\!\! -}\mathop {B{\rm 0}}\nolimits_u^ + ,\;v_B = 18 - 21 )$ and bound–bound ${\rm I}_2 ( {\mathop 0\nolimits_g^ + , \mathop 1\nolimits_u (bb) \buildrel{{\scriptstyle hv_{f}}}\over{\longleftarrow \!\!\!\! - \!\!\! - \!\!\! -}\mathop {B{\rm 0}}\nolimits_u^ + , v_B = 21,\;J_B } )$ transitions at a fundamental harmonic of the Nd:YAG laser

“…We successfully utilize three-step two-and three-color schemes of the population of ungerade D0 + u and gerade β1 g and D 2 g iodine state selected rovibronic levels, D, v D , J D , β, v β , J β and D , v D , J D via rovibronic states of intermediate B and 0 + g , 1u(bb) states (both latter correlate with the third dissociation limit, I( 2 P 1/2 + 2 P 1/2 ) (bb)) or their van der Waals complexes [16][17][18][19][20][21]. The 0 + g (bb) ← B0 + u transition is an EDA one, whereas the mechanism of the 1 u (bb) ← B0 + u electric dipole forbidden transition in pure iodine vapor is unknown at the moment (see [22] and references therein).…”