Rotationally resolved spectrum of the band of HCBr

Hall, Gregory E.; Sears, Trevor J.; Yu, Hua‐Gen

doi:10.1016/j.jms.2005.08.017

Cited by 19 publications

(7 citation statements)

References 26 publications

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“…The MRCI vertical excitation energy (1.80 eV) and dissociation energy (2.02 eV) have no literature comparison. Lastly, the recently proposed 2 1 A state was predicted to have an adiabatic transition energy of 2.59 eV by the Sears group using the MRCI/cc-VTZ method [28]. We predict a value of <3.26 eV.…”

Section: Literature Comparisons and Discussionmentioning

confidence: 70%

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Multireference configuration interaction studies of HCBr

Burrill¹,

Grein²

2008

Can. J. Phys.

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Multireference configuration interaction (MRCI) potential curves were obtained for six 1 A , 1 A , 3 A , and 3 A states of bromomethylene, HCBr, as functions of R CBr for bond angles of 102.9 • and 130 • , and as functions of the bond angle for R CBr = 1.8682 Å. A (6.61) (with estimated upper limits to the adiabatic transition energies in eV in parentheses), as well as several 5s and 6s Rydberg states, were found to be stable or metastable. Estimated spectroscopic constants for bound and metastable states, as well as vertical excitation energies for repulsive or quasi repulsive states are listed. The CH+Br dissociation energy of the ground state is about 3.5 eV, and 3.3 eV for a 3 A , whereas it is about 3.6 eV for CBr-H dissociation. It follows that photodissociation of ground-state HCBr by sunlight (up to 4.4 eV) can lead to both Br and H radicals. Photodissociation via several low-lying states is also possible.Résumé : Nous avons obtenu les courbes de potentiel pour les états 1 A , 1 A , 3 A et 3 A du bromoéthylène, HCBr, en fonction de R CBr pour les angles de lien de 102.9 et 130 degrés et comme fonction de l'angle de lien pour R CBr = 1, 8682 Å. En plus des états bien connus X 1 A , a 3 A et A 1 A , nous avons trouvé comme étant stables ou métastables les états 2 1 A (6,61) (les quantités entre parenthèse donnant en eV la limite supérieure des énergies de transition adiabatique), ainsi que plusieurs états de Rydberg 5s et 6s. Nous présentons la liste d'un estimé des constantes spectroscopiques pour les états liés et métastables, ainsi que des énergies d'excitation verticale pour les états répulsifs ou quasi-répulsifs. L'énergie de dissociation pour le fondamental de CH+Br est environ 3,5 et 3,3 eV pour l'état a 3 A , alors qu'il est 3,6 eV pour la dissociation de CBr-H. Il s'ensuit que la photodissociation du fondamental de HCBr par la lumière solaire (jusqu'à 4,4 eV) peut mener aux radicaux Br et H. La photodissociation via plusieurs états de basse énergie est également possible.[Traduit par la Rédaction]

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Section: Literature Comparisons and Discussionmentioning

confidence: 70%

“…Very recently, the Sears group produced another experimental work on HCBr, this time focusing on the visible spectrum rather than the near IR spectrum [28]. Perturbations of parallel bands were attributed to a previously unmentioned B 1 A state.…”

Section: Introductionmentioning

confidence: 99%

Multireference configuration interaction studies of HCBr

Burrill¹,

Grein²

2008

Can. J. Phys.

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“…Over the past decade, several experimental groups, including our own, initiated detailed spectroscopic studies of the monohalocarbenes. − ,− ,− ,− Despite this large body of work, only last year was the spectrum of an iodocarbene, :CHI, reported by us after an extensive effort . The vibronic assignments in the electronic spectrum were unclear, as only bands lying quite far above the origin were measured, yet this work established a singlet multiplicity for the ground state and gave a lower limit on the singlet−triplet gap of 3.76 kcal mol −1 , using a deperturbation analysis of SVL emission spectra.…”

Section: Introductionmentioning

confidence: 98%

Fluorescence Excitation and Emission Spectroscopy of the X̃¹A′ → Ã¹A′′ System of CHI and CDI

2009

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We report on the first detailed studies of the spectroscopy of an iodocarbene, measuring fluorescence excitation and emission spectra of the X1A' --> A1A'' system of :CHI and the deuterated isotopomer :CDI. Due to similar bending and C-I stretching frequencies in the upper state, fluorescence excitation spectra of :CHI show polyads composed of members of the 2(0)(n-x)3(0)x progressions with x = 0-3. For :CDI, only progressions with x = 0, 1 are observed. Extrapolation of the 20n term energies for both isotopomers to a common origin places the electronic origin of the X1A' --> A1A'' system near 10500 cm-1, in good agreement with theoretical predictions. Rotational analysis of the 16 observed bands for CHI and 13 observed bands for :CDI yields rotational constants for the upper and lower states that are also in good agreement with theory. To investigate the controversial issue of the ground state multiplicity of :CHI, we measured single vibronic level emission spectra from many A1A'' levels. These spectra show conclusively that the ground state is a singlet, as for both isotopomers the ã3A'' origin is observed, lying well above the origin of the X1A' state. At energies above the ã3A'' origin, the spin-orbit mixing is so severe that few vibrational assignments can be made. Analysis of the emission spectra provides a lower limit on the singlet-triplet gap of 4.1 kcal mol-1, in excellent agreement with theoretical predictions.

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“…Coupling of the triplet to the singlet groundX 1 A ′ state is important, as the states cross close to the minimum of each surface. This interaction was found to play a major role in the perturbation of vibrational levels of the interacting states, 5,6,[12][13][14][15][16][17][18][19][20][21] which has been examined in detail using laser-induced fluorescence (LIF), single vibronic level emission (SVLE) spectroscopy, [22][23][24][25][26][27][28][29][30][31][32] and stimulated emission pumping (SEP) spectroscopy. 33,34 While on one hand these studies have been remarkably successful in providing estimates for the singlet-triplet gaps, which have been compared with the predictions of ab initio and Density Functional Theory (DFT) calculations, 18, and revealed perturbations of the singlet level structure by SO-coupling, which have been analyzed in some detail, on the other hand, a global analysis of the SO-coupling in these systems has not been performed.…”

Section: Introductionmentioning

confidence: 99%

Towards a global model of spin-orbit coupling in the halocarbenes

Nyambo

Karshenas

Reid

et al. 2015

The Journal of Chemical Physics

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We report a global analysis of spin-orbit coupling in the mono-halocarbenes, CH(D)X, where X = Cl, Br, and I. These are model systems for examining carbene singlet-triplet energy gaps and spin-orbit coupling. Over the past decade, rich data sets collected using single vibronic level emission spectroscopy and stimulated emission pumping spectroscopy have yielded much information on the ground vibrational level structure and clearly demonstrated the presence of perturbations involving the low-lying triplet state. To model these interactions globally, we compare two approaches. First, we employ a diabatic treatment of the spin-orbit coupling, where the coupling matrix elements are written in terms of a purely electronic spin-orbit matrix element which is independent of nuclear coordinates, and an integral representing the overlap of the singlet and triplet vibrational wavefunctions. In this way, the structures, harmonic frequencies, and normal mode displacements from ab initio calculations were used to calculate the vibrational overlaps of the singlet and triplet state levels, including the full effects of Duschinsky mixing. These calculations have allowed many new assignments to be made, particularly for CHI, and provided spin-orbit coupling parameters and values for the singlet-triplet gaps. In a second approach, we have computed and fit full geometry dependent spin-orbit coupling surfaces and used them to compute matrix elements without the product form approximation. Those matrix elements were used in similar fits varying the anharmonic constants and singlet-triplet gap to reproduce the experimental levels. The derived spin-orbit parameters for carbenes CHX (X = Cl, Br, and I) show an excellent linear correlation with the atomic spin-orbit constant of the corresponding halogen, indicating that the spin-orbit coupling in the carbenes is consistently around 14% of the atomic value.

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Rotationally resolved spectrum of the band of HCBr

Cited by 19 publications

References 26 publications

Multireference configuration interaction studies of HCBr

Multireference configuration interaction studies of HCBr

Fluorescence Excitation and Emission Spectroscopy of the X̃¹A′ → Ã¹A′′ System of CHI and CDI

Towards a global model of spin-orbit coupling in the halocarbenes

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Rotationally resolved spectrum of the band of HCBr

Cited by 19 publications

References 26 publications

Multireference configuration interaction studies of HCBr

Multireference configuration interaction studies of HCBr

Fluorescence Excitation and Emission Spectroscopy of the X̃1A′ → Ã1A′′ System of CHI and CDI

Towards a global model of spin-orbit coupling in the halocarbenes

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Product

Resources

About

Fluorescence Excitation and Emission Spectroscopy of the X̃¹A′ → Ã¹A′′ System of CHI and CDI