Photofragment Imaging of HNCO Decomposition at 210 nm: the Primary NH(<i>a</i>1)+CO(<i>X</i>1+) Channel

Wang, Hua; Liu, Shi Lin; Liu, Jie; Wang, Feng Yan; Jiang, Bo; Yang, Xueming

doi:10.1088/1674-0068/20/04/388-394

Cited by 15 publications

(16 citation statements)

References 29 publications

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“…Such phenomenon has been seen previously in HNCO photodissociation at 210 nm 26 and can be explained by a nonaxial recoil impact model. 41 In the present study, the most interesting observation is the bimodal rotational distribution of CO(v = 0) that correlates to 1 NH(v|j).…”

Section: Resultssupporting

confidence: 79%

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Imaging the Pair-Correlated HNCO Photodissociation: The NH(a¹Δ) + CO(X¹Σ⁺) Channel

et al. 2014

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The NH(a(1)Δ) + CO(X(1)Σ(+)) product channel for the photodissociation of HNCO at 201 nm was investigated using the sliced velocity map ion imaging technique with the detection of NH(a(1)Δ) products via (2 + 1) resonance enhanced multiphoton ionization (REMPI). Images were measured for the NH(a(1)Δ) rotational states in the ground and vibrational excited states (v = 0 and 1). Correlation between the NH(a(1)Δ) and CO rovibrational state distributions were determined from these images. Experimental results show that the vibrational distribution of the CO fragment in the NH(a(1)Δ) + CO(X(1)Σ(+)) channel peaks at v = 1. The negative anisotropy parameter measured for the NH(a(1)Δ) (v = 0 and 1|j) products indicates a direct dissociation process for the N-C bond cleavage in the S1 state. A bimodal CO rotational distribution was observed, suggesting that HNCO dissociates in the S1 state in two distinctive pathways.

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Section: Resultssupporting

confidence: 79%

“…Wang et al 26 investigated channel (3) at 210 nm using the sliced velocity map ion imaging technique for CO fragment detection. Fujimoto et al 27 detected CO(v) at 193.3 nm and levels up to v = 4 were observed.…”

Section: Introductionmentioning

confidence: 99%

Imaging the Pair-Correlated HNCO Photodissociation: The NH(a¹Δ) + CO(X¹Σ⁺) Channel

et al. 2014

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“…They found cold 1 NH rotational distribution with hot CO distribution. Such a trend has also been reported by Wang et al 22 following the excitation at 210 nm by using ion velocity slice imaging technique. They suggested impulsive direct and vertical dissociation process of HNCO on the singlet state at 210 nm.…”

Section: ■ Introductionsupporting

confidence: 81%

Competition between Direct and Indirect Dissociation Pathways in Ultraviolet Photodissociation of HNCO

Dorenkamp

et al. 2013

J. Phys. Chem. A

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Photodissociation dynamics of HNCO at photolysis wavelengths between 200 and 240 nm have been studied using the Hatom Rydberg tagging time-of-flight technique. Product translational energy distributions and angular distributions have been determined. At low photon energy excitation, the product translational energy distribution is nearly statistical and the angular distribution is isotropic, which is consistent with an indirect dissociation mechanism, i.e., internal conversion from S 1 to S 0 surface and dissociation on S 0 surface. As the photon energy increases, a direct dissociation pathway on S 1 surface opens up. The product translational energy distribution appears to be quite nonstatistical and the product angular distribution is anisotropic. The fraction of direct dissociation pathway is determined to be 36 ± 5% at 202.67 nm photolysis. Vibrational structures are observed in both direct and indirect dissociation pathways, which can be assigned to the NCO bending mode excitation with some stretching excitation. ■ INTRODUCTIONPhotodissociation of isocyanic acid (HNCO) has attracted much attention over the last thirty years because of its importance in combustion and atmospheric chemistry. In addition, HNCO can serve as a benchmark system for understanding the multiple decomposition pathways in a simple four-atom molecule, such as internal conversion (IC), intersystem crossing (ISC), and direct dissociation processes. The first UV absorption band of HNCO is known to extend from 280 nm to wavelengths shorter than 200 nm. It has been analyzed by Dixon and Kirby 1 and by Rabalais et al. 2,3 and assigned to an S 1 ( 1 A″) ← S 0 ( 1 A′) transition to the first singlet state. Photodissociation dynamics of HNCO in the S 1 state have been revealed by dozens of experimental and theoretical studies and are found to be quite complicated, because at least three electronic states (S 0 , S 1 , and T 1 ) participate in the dissociation. 4−11 There are three thermodynamically allowed dissociation channels from the S 1 state:30060 25 cm The energetically lowest energy channel 1 is a spin-forbidden dissociation pathway and has only recently been observed by direct detection of 3 NH in 260−217 nm photolysis. Zyrianov et al. 7 suggested that channel 1 requires ISC by which HNCO eventually reaches the triplet state T 1 and then dissociates. Theoretical studies 12 showed that the dissociation of this channel follows both the IC and ISC processes from S 1 to S 0 and then from S 0 to T 1 . Although its exact quantum yield has not been determined, channel 1 appears to be the major channel in the region just above the threshold of channel 2. 13,14 The dynamics of channel 3 have been extensively studied at several different wavelengths. [15][16][17][18][19][20] measured the 1 NH state distribution by using laser-induced fluorescence (LIF) following 193.3 nm photodissociation. They found that NH(a 1 Δ) was formed to be predominantly in v = 0, with rotational excitation accounting for about 8% of the available energy. Fujimot...

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“…Up-to-date experimental investigations of HNCO photodissociation have been performed by Yang and co-workers. , In 2007, they measured pair-correlated angular and kinetic energy distributions (KEDs) for the NH(a 1 Δ) + CO(X 1 Σ + ) channel using velocity map imaging (VMI), where CO was state-selectively detected by (2 + 1) resonance-enhanced multiphoton ionization (REMPI). They proved the predominance of the formation of the previous products following photon excitation at 210 nm, with coproduct NH(a 1 Δ) ≡ 1 NH in the vibrational ground state. Rotational state distributions of 1 NH were deduced from the KEDs, while state-resolved anisotropy parameters (APs) were deduced from angular distributions.…”

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confidence: 99%

“…None of the previous theoretical treatments of the title reaction were performed in full-dimensionality. , Instead, HNCO was kept planar throughout its fragmentation. For the sake of realism, however, out-of-plane motions should be taken into account.…”

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confidence: 99%

Full-Dimensional Theory of Pair-Correlated HNCO Photofragmentation

Bonnet

Linguerri

Hochlaf

et al. 2017

J. Phys. Chem. Lett.

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Full-dimensional semiclassical dynamical calculations combining classical paths and Bohr quantization of product internal motions are reported for the prototype photofragmentation of isocyanic acid in the S state. These calculations allow one to closely reproduce for the first time key features of state-of-the-art imaging measurements at photolysis wavelengths of 201 and 210 nm while providing insight into the underlying dissociation mechanism. Quantum scattering calculations being beyond reach for most polyatomic fissions, pair-correlated data on these processes are much more often measured than predicted. Our theoretical approach can be used to fill this gap.

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Photofragment Imaging of HNCO Decomposition at 210 nm: the Primary NH(a1)+CO(X1+) Channel

Cited by 15 publications

References 29 publications

Imaging the Pair-Correlated HNCO Photodissociation: The NH(a¹Δ) + CO(X¹Σ⁺) Channel

Imaging the Pair-Correlated HNCO Photodissociation: The NH(a¹Δ) + CO(X¹Σ⁺) Channel

Competition between Direct and Indirect Dissociation Pathways in Ultraviolet Photodissociation of HNCO

Full-Dimensional Theory of Pair-Correlated HNCO Photofragmentation

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Photofragment Imaging of HNCO Decomposition at 210 nm: the Primary NH(a1)+CO(X1+) Channel

Cited by 15 publications

References 29 publications

Imaging the Pair-Correlated HNCO Photodissociation: The NH(a1Δ) + CO(X1Σ+) Channel

Imaging the Pair-Correlated HNCO Photodissociation: The NH(a1Δ) + CO(X1Σ+) Channel

Competition between Direct and Indirect Dissociation Pathways in Ultraviolet Photodissociation of HNCO

Full-Dimensional Theory of Pair-Correlated HNCO Photofragmentation

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Imaging the Pair-Correlated HNCO Photodissociation: The NH(a¹Δ) + CO(X¹Σ⁺) Channel

Imaging the Pair-Correlated HNCO Photodissociation: The NH(a¹Δ) + CO(X¹Σ⁺) Channel