The ν1 and 3ν1 bands of HNCO

Carlotti, M.; Lonardo, G. Di; Galloni, G.; Trombetti, A.

doi:10.1016/0022-2852(76)90349-0

Cited by 15 publications

(7 citation statements)

References 11 publications

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“…Absorption spectroscopy of the 3ν 1 state reveals several vibrational couplings throughout the spectrum, most notably a moderately strong two-state interaction for the K ) 3, J ) 4-10 angular momentum states. 14 Because these pairs of perturbed eigenstates are well separated in energy, selective excitation of states with different amounts of the perturbing vibration is possible. Our approach is to use the information from absorption spectroscopy to characterize the mixed vibrational states and to examine the effects of selective excitation on both bimolecular reaction and photodissociation dynamics using action spectroscopy.…”

Section: Introductionmentioning

confidence: 99%

Controlling the Bimolecular Reaction and Photodissociation of HNCO through Selective Excitation of Perturbed Vibrational States

et al. 2000

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Selective reaction or photodissociation of isocyanic acid (HNCO) molecules in well-characterized vibrational eigenstates is a means of controlling their chemistry. The key to the measurements is the characterization of their vibrational states by absorption spectroscopy and the determination of their reaction efficiency by action spectroscopy. Absorption spectroscopy and theoretical calculations on states in the region of three quanta of the N−H stretching excitation (3ν1) of HNCO identify couplings between the bright N−H stretching state and states that have one or more quanta of N−C−O bending excitation. Bimolecular reaction action spectroscopy, which monitors the yield of NCO from the reaction of Cl atoms with HNCO, and photodissociation action spectroscopy, which monitors the production of 1NH following S1 ← S0 excitation in HNCO, measure the relative reaction and photodissociation cross sections for the mixed vibrational eigenstates having rotational quantum numbers K = 3 and J = 6 and 7. The measurements and analysis show that the perturbing zero-order state is substantially less reactive than the bright state but has a photodissociation cross section that is much larger than that of the bright state. Bending excitation of N−C−O strongly influences both the reaction and photodissociation, hindering bimolecular reaction but promoting photodissociation.

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Section: Introductionmentioning

confidence: 99%

Controlling the Bimolecular Reaction and Photodissociation of HNCO through Selective Excitation of Perturbed Vibrational States

et al. 2000

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“…Absorption spectroscopy, which finds that states with Kϭ1 and 4 ͑except for high J states͒ are unperturbed while Kϭ0, 2, and 3 states are all perturbed, suggests a more reasonable explanation. 16,17 The change in the vibrational character of the eigenstates with K is probably the important difference among the states. Because the bright and dark zero-order states have different a-axis rotational constants, their separation in energy, and, consequently, their mixing changes with K. The largely unperturbed vibrational eigenstates ͑those for Kϭ1 and 4͒ are primarily the N-H stretching zero-order state and react efficiently, but the more strongly perturbed eigenstates ͑those for Kϭ0, 2, and 3͒ contain motions along coordinates other than the N-H stretch and react less efficiently.…”

Section: Discussionmentioning

confidence: 99%

“…For example, the Kϭ1 and Kϭ4 subbands are unperturbed for the J states we consider, but the Kϭ0, 2, and 3 subbands are perturbed, each one probably by a different state. 16,17 The presence of both perturbed and unperturbed vibrational states is useful for examining the reactivity of mixed eigenstates. Furthermore, the absorption spectroscopy of the Kϭ3 subband of 3 1 reveals moderate coupling over a small range from Jϭ5 to Jϭ12 with a matrix element of ͉V͉ Ϸ0.035 cm Ϫ1 to a state that is likely to have two quanta of N-H stretch and several quanta of other vibrations.…”

Section: Introductionmentioning

confidence: 99%

“…Furthermore, the absorption spectroscopy of the Kϭ3 subband of 3 1 reveals moderate coupling over a small range from Jϭ5 to Jϭ12 with a matrix element of ͉V͉ Ϸ0.035 cm Ϫ1 to a state that is likely to have two quanta of N-H stretch and several quanta of other vibrations. 16,17 By studying these states in detail, we can extract the relative reactivity of the perturbing state and infer the effect that simple vibrational motions, such as N-H stretching and N-C-O bending, have on the course of the reaction.…”

Section: Introductionmentioning

confidence: 99%

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Using stretching and bending vibrations to direct the reaction of Cl atoms with isocyanic acid (HNCO)

Woods

Cheatum

Crim

1999

The Journal of Chemical Physics

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“…These transitions add 10 127 cm Ϫ1 of energy to the molecule and terminate in the rovibrational states K a ϭ1, Jϭ14 and K a ϭ2, Jϭ13 in S 0 , which have energies of 10 245 and 10 302 cm Ϫ1 , respectively. 33 Because transitions to the K a ϭ2 state are much more intense in the vibrational overtone action spectrum, we use the energy of that state in the discussion below.…”

Section: Methodsmentioning

confidence: 99%

Relative product yields in the one-photon and vibrationally mediated photolysis of isocyanic acid (HNCO)

Berghout

Hsieh

Crim

2001

The Journal of Chemical Physics

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Using stretching and bending vibrations to direct the reaction of Cl atoms with isocyanic acid (HNCO) Efficient collisional vibrational relaxation of triplet state molecules: Pyrazine deuteration and methylation effects Direct observation of all three photofragmentation channels of HNCO gives the relative yields of 3 NHϩCO, HϩNCO, and 1 NHϩCO at nine different photolysis energies for both thermal and vibrationally excited molecules. Each higher energy channel dominates as it becomes accessible, but vibrational excitation changes the relative yield of 1 NH markedly. Photolysis of HNCO(3 1 ) at the same total energy yields up to 2.5 times more NCO with a corresponding reduction in 1 NH. The relative yield of 3 NH and NCO, however, is indifferent to vibrational excitation. The dependence of the yields on vibrational excitation supports a picture in which direct decomposition on the S 1 surface produces 1 NHϩCO and in which internal conversion to S 0 leads to HϩNCO, by spin-allowed unimolecular decay, and to 3 NHϩCO, by intersystem crossing and decomposition on T 1 . The observed vibrational enhancement of the NCO yield is consistent with vibrational excitation impeding the decomposition to 1 NHϩCO on S 1 and, thus, increasing the number of molecules that cross to S 0 and decay to HϩNCO.

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The ν1 and 3ν1 bands of HNCO

Cited by 15 publications

References 11 publications

Controlling the Bimolecular Reaction and Photodissociation of HNCO through Selective Excitation of Perturbed Vibrational States

Controlling the Bimolecular Reaction and Photodissociation of HNCO through Selective Excitation of Perturbed Vibrational States

Using stretching and bending vibrations to direct the reaction of Cl atoms with isocyanic acid (HNCO)

Relative product yields in the one-photon and vibrationally mediated photolysis of isocyanic acid (HNCO)

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