Rotational analysis of the O−O band of the first singletπ *-n system ofcis glyoxal-d1

“…Glyoxal, HCOCOH, has been of interest to spectroscopists and physical chemists since even before the 1970s, when the first analyses of its visible spectrum were made by Ramsay and co-workers. − In the intervening years a great deal of information has been obtained about both the coupling between the lowest excited singlet state and the lowest triplet state of the molecule − and about its high-resolution, Doppler-free spectrum . The fluorescence quantum yield for low-lying vibrational levels of the 1 A u state is on the order of 50%; internal conversion from the S 1 to the S 0 surface is the nonradiative process .…”

Section: Introductionmentioning

confidence: 99%

H₂ Production in the 440-nm Photodissociation of Glyoxal

et al. 1999

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H 2 has been detected following the photolysis of glyoxal at 440 nm using the techniques of vacuum ultraviolet laser-induced fluorescence and (2 + 1) resonance enhanced multiphoton ionization. It is thus confirmed that a fraction of the glyoxal excited at this wavelength dissociates into three photofragments: HCOCOH f H 2 + 2 CO. The most populated vibrational level of those observed was H 2 (V ) 1), and in this level rotational states from J ) 0-9 were detected. Doppler profiles of these lines provide estimates of the translational energy and show a v||J correlation. Of the available energy to the H 2 + 2CO products, 3.1% appears as rotational energy in H 2 (V ) 1), 17.8% appears as the H 2 (V ) 1) vibration, and 46.8% appears as H 2 (V ) 1) translation. Excitation of the 7 0 2 band produces somewhat more of the H 2 + 2CO channel than does excitation of the 0 0 0 , 5 0 1 , or 8 0 1 bands. These observations are consistent with a model in which transfcis isomerization precedes dissociation. Rotational excitation with v||J is caused by the V 7 torsional motion. The small degree of rotational excitation, the production of H 2 in V ) 1 and V ) 2, and the translational energy distribution are all consistent with ab initio calculations of the transition state structure.

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“…Extensive high resolution spectroscopic studies have been made by Ramsay and coworkers. 4 -6 .In addition, they made the first observation of the cis form of glyoxal and identified the 1 B 1 excited state 0 [7][8][9] in rotational analysis of a band at 4875 A. This state is associat~d with an n (a 1 ) ~ n* (b 1 ) excitation and a 3 a 1 state is presumed to occur in the same region.…”

Section: Introductionmentioning

confidence: 99%

Electronic structure of dicarbonyls. Glyoxal excited states

Dykstra¹,

Schaefer²

1976

J. Am. Chem. Soc.

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Excited ~lectronic states of glyoxal, (CH0) 2 , have been studied by ab initio self-consistent field (SCF) methods using a double-zeta basis set of contracted gaussian functions. The vertical excitation energies from the optimum ground state geometry were determined for 20 trans and 20 cis excited states. These included all singlet and triplet n+7T* and 7T+TI'* excitations and the lowest n+o* excitations. Geometry optimization was performed for the three lowest cis and trans states. Two 3 very low-lying unobserved triplet states, trans Bu and cis 3 B 2 , are predicted by these calculations to be within about 15;000 cm-l of the corresponding ground states, making them the lowest excited states of glyoxal. The next lowest lying states 3 1 1 were the observed trans Au' Au and cis B 1 , for which the geometry optimization provides a basis for comparison with experi-';'(ment. The ekperimentally observed states arise from an n 7 TI excitation, but surprisingly the lowest triplets arise from ~~ * n + 1r excitations. The geometry of these n 7 n triplets is strikingly different f:tom that of the ground state and is in closer correspondence with a biradical structure. '.

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Rotational analysis of the O−O band of the first singletπ *-n system ofcis glyoxal-d1

Cited by 35 publications

References 8 publications

Electronic structure of dicarbonyls. Ground state of glyoxal

Electronic structure of dicarbonyls. Ground state of glyoxal

H₂ Production in the 440-nm Photodissociation of Glyoxal

Electronic structure of dicarbonyls. Glyoxal excited states

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Rotational analysis of the O−O band of the first singletπ *-n system ofcis glyoxal-d1

Cited by 35 publications

References 8 publications

Electronic structure of dicarbonyls. Ground state of glyoxal

Electronic structure of dicarbonyls. Ground state of glyoxal

H2 Production in the 440-nm Photodissociation of Glyoxal

Electronic structure of dicarbonyls. Glyoxal excited states

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H₂ Production in the 440-nm Photodissociation of Glyoxal