Overtone-induced dissociation and isomerization dynamics of the hydroxymethyl radical (CH2OH and CD2OH). II. Velocity map imaging studies

Ryazanov, Mikhail; Rodrigo, Chirantha P.; Reisler, H.

doi:10.1063/1.3685899

Cited by 29 publications

(53 citation statements)

References 45 publications

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“…1. As will be shown in Paper II, 18 the theoretical values for the CH 2 OH → CH 2 O + H, CD 2 OH → CD 2 O + H, and CD 2 OH → CHDO + D channels are in excellent agreement with the experimental ones. The CH 2 OH dissociation energy is also in excellent agreement with the calculations of Ref.…”

Section: A Pes Vibrational Energies and Key Energeticssupporting

confidence: 77%

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Overtone-induced dissociation and isomerization dynamics of the hydroxymethyl radical (CH2OH and CD2OH). I. A theoretical study

Kamarchik

Rodrigo

Bowman

et al. 2012

The Journal of Chemical Physics

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The dissociation of the hydroxymethyl radical, CH(2)OH, and its isotopolog, CD(2)OH, following the excitation of high OH stretch overtones is studied by quasi-classical molecular dynamics calculations using a global potential energy surface (PES) fitted to ab initio calculations. The PES includes CH(2)OH and CH(3)O minima, dissociation products, and all relevant barriers. Its analysis shows that the transition states for OH bond fission and isomerization are both very close in energy to the excited vibrational levels reached in recent experiments and involve significant geometry changes relative to the CH(2)OH equilibrium structure. The energies of key stationary points are refined using high-level electronic structure calculations. Vibrational energies and wavefunctions are computed by coupled anharmonic vibrational calculations. They show that high OH-stretch overtones are mixed with other modes. Consequently, trajectory calculations carried out at energies about ~3000 cm(-1) above the barriers reveal that despite initial excitation of the OH stretch, the direct OH bond fission is relatively slow (10 ps) and a considerable fraction of the radicals undergoes isomerization to the methoxy radical. The computed dissociation energies are: D(0)(CH(2)OH → CH(2)O + H) = 10,188 cm(-1), D(0)(CD(2)OH → CD(2)O + H) = 10,167 cm(-1), D(0)(CD(2)OH → CHDO + D) = 10,787 cm(-1). All are in excellent agreement with the experimental results. For CH(2)OH, the barriers for the direct OH bond fission and isomerization are: 14,205 and 13,839 cm(-1), respectively.

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Section: A Pes Vibrational Energies and Key Energeticssupporting

confidence: 77%

“…In the paper following this one (Paper II, Ref. 18), new experimental results using velocity map imaging are presented, which give evidence for the participation of direct OH bond fission and isomerization in the overtone-induced predissociation of the hydroxymethyl radical.…”

Section: Introductionmentioning

confidence: 99%

Overtone-induced dissociation and isomerization dynamics of the hydroxymethyl radical (CH2OH and CD2OH). I. A theoretical study

Kamarchik

Rodrigo

Bowman

et al. 2012

The Journal of Chemical Physics

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“…39,45,48 We have demonstrated vibrational resolution for H 2 CO and HCOH(D) cofragments generated in CH 2 OH(D) dissociation by measuring the kinetic energy distributions (KEDs) of H(D) products. 11,39 II. EXPERIMENTAL DETAILS The experimental arrangement for generating hyrodroxymethyl radicals in a molecular beam and detection of H(D) photofragments using SVMI was described in detail elsewhere, 39,45,48 and therefore only a brief description is given below.…”

Section: Introductionmentioning

confidence: 99%

Imaging Studies of Excited and Dissociative States of Hydroxymethylene Produced in the Photodissociation of the Hydroxymethyl Radical

2014

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Rotational, vibrational, and electronic states of formaldehyde and cis-hydroxymethylene products generated in the photodissociation of the hydroxymethyl radical are investigated by sliced velocity map imaging (SVMI) following excitation of the radical to its 3px and 3pz Rydberg states. SVMI of H and D photofragments is essential in these studies because it allows zooming in on low-velocity regions of the images where small threshold signals can be identified. With CH2OD precursors, formaldehyde and hydroxymethylene products are examined separately by monitoring D and H, respectively. Whereas the main dissociation channels lead to formaldehyde and cis-hydroxymethylene in their ground electronic states, at higher excitation energies the kinetic energy distributions (KEDs) of H and D photofragments exhibit additional small peaks, which are assigned as triplet states of formaldehyde and hydroxymethylene. Results obtained with deuterated isotopologs of CH2OH demonstrate that the yield of the triplet state of formaldehyde decreases upon increasing deuteration, suggesting that the conical intersection seams that govern the dynamics depend on the degree of deuteration. The rotational excitation of cis-hydroxymethylene depends on the excited Rydberg state of CH2OD and is lower in dissociation via the 3pz state than via the lower lying 3px and 3s states. Vibrational excitation of cis-HCOD, which spans the entire allowed internal energy range, consists mostly of the CO-stretch and in-plane bend modes. When the internal energy of cis-HCOD exceeds the dissociation threshold to D + HCO, slow D and H photofragments deriving from secondary dissociation are observed. The yields of these H and D fragments are comparable, and we propose that they are generated via prior isomerization of cis-HCOD to HDCO.

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“…Experimental and computational studies of ground and excited state photodissociation of CH 2 OH have been reported, [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16] as have studies of CH 3 CHOH. 17,18 Computational studies 10 complementing experimental studies 15 of the ground state photodissociation CH 2 OH(X 2 A) + hv → CH 2 O(X 1 A 1 ) + H have been reported. The computational work employed two high quality adiabatic potential energy surfaces (PESs), developed in that study 10 denoted KRBRK below.…”

Section: Introductionmentioning

confidence: 99%

Multistate, multichannel coupled diabatic state representations of adiabatic states coupled by conical intersections. CH2OH photodissociation

Malbon

Yarkony

2017

The Journal of Chemical Physics

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A coupled diabatic state representation, H, of the 1, 2, 3 A states of CHOH suitable for the description of the three channel, three state photodissociation process CHOH(1 A) + hv → CHOH(2, 3 A) → CHO(X, A) + H, cis-CHOH + H, trans-CHOH + H, is reported. The representation is based on electronic structure data (energies, energy gradients, and derivative couplings) obtained exclusively from multireference configuration interaction single and double excitation wave functions. Diabat shifting is employed to improve the representation's agreement with accurate experimental energetics. A careful analysis of the numerous minima, saddle points, and conical intersection seams is reported. The computed T(3 A) ∼ 35 220 cm is in excellent agreement with the experimental estimate of 35 053 cm, and the computed channel dissociation energies, D, for CHO 9453 (10 160), cis-HCOH 30 310.2 (29 923), and trans-HCOH 28 799 (28 391) cm are in good accord with the measured values given parenthetically. These accurate energetics over a wide range of nuclear configurations strongly support the ability of this H to enable quality simulations of nonadiabatic dynamics.

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Overtone-induced dissociation and isomerization dynamics of the hydroxymethyl radical (CH2OH and CD2OH). II. Velocity map imaging studies

Cited by 29 publications

References 45 publications

Overtone-induced dissociation and isomerization dynamics of the hydroxymethyl radical (CH2OH and CD2OH). I. A theoretical study

Overtone-induced dissociation and isomerization dynamics of the hydroxymethyl radical (CH2OH and CD2OH). I. A theoretical study

Imaging Studies of Excited and Dissociative States of Hydroxymethylene Produced in the Photodissociation of the Hydroxymethyl Radical

Multistate, multichannel coupled diabatic state representations of adiabatic states coupled by conical intersections. CH2OH photodissociation

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