Structural Distortion of CH3I in an Ion-Dipole Precursor Complex

Photoelectron imaging results are presented for I(-)[middle dot]X cluster anions (X = CO(2), C(4)H(5)N [pyrrole], (CH(3))(2)CO, CH(3)NO(2)). The available detachment channels are labeled according to the neutral iodine atom states produced (channel I ≡ (2)P(3/2) and channel II ≡ (2)P(1/2)). At photon energies in the vicinity of the channel II threshold these data are compared to previously reported results for I(-)[middle dot]X (X = CH(3)CN, CH(3)Cl, CH(3)Br, and H(2)O). In particular, these results show a strong connection between the dipole moment of the solvent molecule and the behavior of the channel I photoelectron angular distributions in this region, which is consistent with an electronic autodetachment process. The evolution of the channel II:channel I branching ratios in this excitation regime supports this contention.

Section: Introductionmentioning

confidence: 80%

Inter-channel effects in monosolvated atomic iodide cluster anion detachment: Correlation of the anisotropy parameter with solvent dipole moment

Mbaiwa

Dao

Holtgrewe

et al. 2012

“…Ab initio MP2 calculations, performed via QCHEM ͑Ref. 78 The C-X bond in I − ·CH 3 I is elongated by 1.5%, while the corresponding bonds in the I − ·CH 3 Br and I − ·CH 3 Cl are elongated by 1.6% and 1.7%, respectively. 75͒ basis sets, reveal a slight distortion of the methyl halide bonds.…”

Section: Resultsmentioning

confidence: 99%

“…78 However, the vibrational structure in the I − ·CH 3 I photoelectron spectra of Figs. 78 However, the vibrational structure in the I − ·CH 3 I photoelectron spectra of Figs.…”

Section: B Cluster Anion Vibrational Excitation and Fragmentationmentioning

confidence: 99%

I − ⋅ CH 3 X (X=Cl,Br,I) photodetachment: The effect of electron-molecule interactions in cluster anion photodetachment spectra and angular distributions

Duzor

Wei

Mbaiwa

et al. 2010

The electron kinetic energy dependence of the photoelectron spectra and angular distributions of I(-)⋅CH(3)X (X=Cl,Br,I) cluster anions are measured via velocity mapped imaging at wavelengths between 350 and 270 nm. Processes analogous to those encountered in free CH(3)X-electron interactions are revealed. In particular, the presence and energies of resonances associated with a low lying σ(∗) state have a marked effect on the results of I(-)⋅CH(3)X photoexcitation. These effects (vibrational excitation, product anion production, and alteration of the photoelectron angular distribution) are far more prominent for I(-)⋅CH(3)I. However, in the vicinity of the (2)P(1/2) threshold there is a sharp deviation in the (2)P(3/2) channel angular distribution and an enhancement of the (2)P(3/2) channel vibrational structure of all three cluster anions. These latter effects are specific to the cluster anion environment through the relaxation of the partner excited I atom and subsequent electronic autodetachment.

“…30,32,[37][38][39][40]73,78 The overall behavior of the photoabsorption cross section reflects competition between photofragmentation and photodetachment. 30,32,[37][38][39][40]73,78 The overall behavior of the photoabsorption cross section reflects competition between photofragmentation and photodetachment.…”

Section: Nature Of I à "Ch 3 I Detachmentmentioning

confidence: 99%

Photoelectron anisotropy and channel branching ratios in the detachment of solvated iodide cluster anions

Mabbs

Surber

Sanov

2005

Photoelectron spectra and angular distributions in 267 nm detachment of the I(-)Ar, I(-)H(2)O, I(-)CH(3)I, and I(-)CH(3)CN cluster anions are examined in comparison with bare I(-) using velocity-map photoelectron imaging. In all cases, features are observed that correlate to two channels producing either I((2)P(3/2)) or I((2)P(1/2)). In the photodetachment of I(-) and I(-)Ar, the branching ratios of the (2)P(1/2) and (2)P(3/2) channels are observed to be approximately 0.4, in both cases falling short of the statistical ratio of 0.5. For I(-)H(2)O and I(-)CH(3)I, the (2)P(1/2) to (2)P(3/2) branching ratios are greater by a factor of 1.6 compared to the bare iodide case. The relative enhancement of the (2)P(1/2) channel is attributed to dipole effects on the final-state continuum wave function in the presence of polar solvents. For I(-)CH(3)CN the (2)P(1/2) to (2)P(3/2) ratio falls again, most likely due to the proximity of the detachment threshold in the excited spin-orbit channel. The photoelectron angular distributions in the photodetachment of I(-), I(-)Ar, I(-)H(2)O, and I(-)CH(3)CN are understood within the framework of direct detachment from I(-). Hence, the corresponding anisotropy parameters are modeled using variants of the Cooper-Zare central-potential model for atomic-anion photodetachment. In contrast, I(-)CH(3)I yields nearly isotropic photoelectron angular distributions in both detachment channels. The implications of this anomalous behavior are discussed with reference to alternative mechanisms, affording the solvent molecule an active role in the electron ejection process.