“…The red-shifted feature could correspond to dissociation channels leading to the formation of CH(X), and other channels, such as CHBr 2 + Br, CHBr + 2Br and CHBr + Br 2 , all with release of more energy into translational degrees of freedom, could be responsible for the broad continuum absorption. The ionization potential of bromoform is 10.47 eV, , and some contribution of dissociative photoionization channels to the absorption spectrum is also expected at energies above 10.5 eV. 3 Action spectrum (solid line) of the CH(A) signal was taken with an interference filter in the 10−20 eV excitation energy range.…”
Single photon dissociation of bromoform using synchrotron radiation has been investigated by Fourier transform visible fluorescence spectroscopy (FTVIS). The photodissociation of bromoform in the 12-18 eV energy range results in several products, among which are the CH(A2Delta) and CH(B2Sigma) radicals. Vibrational and rotational state distributions of the CH(A2Delta) are determined from their fluorescence spectra. From the threshold photon energy above which emission from the CH(A2Delta) radicals is observed, the most likely process leading to CH(A) formation is CHBr3 --> CH + 3Br rather than CHBr3 --> CH + Br + Br2. The rotational Boltzmann temperatures in the CH(A --> X) emission spectra for v' = 0 and v' = 1 range between 1570 and 3650 K, depending on the excitation photon energy. From the high rotational excitation, the results suggest that the mechanism for the loss of three bromine atoms is most likely sequential. A small negative emission anisotropy of the CH(A) radicals [(Ipar - Iper)/(Ipar + 2Iper) = -0.024 +/- 0.005] is constant across the action spectrum; a small net absorption dipole of CHBr3 in the vacuum ultraviolet is parallel to the 3-fold symmetry axis of the CHBr3 molecule. The state distributions of the CH(A2Delta) radicals from multiphoton dissociation of bromoform using the 266 nm output (three photons) of a femtosecond laser (Boltzmann temperatures: T(v'=0)(rot)= 4250 +/- 300 K; T(v'=1)(rot)= 3100 +/- 550 K) are compared to those from the single photon dissociation results (Boltzmann temperatures: T(v'=0)(rot)= 3650 +/- 150 K; T(v'=1)(rot)= 2400 +/- 200 K) at the same total excitation energy under collision free conditions. The analysis of the CH(A) rotational populations shows hotter rotational populations for the femtosecond experiment, also suggesting sequential dissociation of the bromoform in the femtosecond experiment. The duration of the femtosecond laser pulse is approximately 180 fs, setting a limit on the time scales for the multiple dissociations.
“…The red-shifted feature could correspond to dissociation channels leading to the formation of CH(X), and other channels, such as CHBr 2 + Br, CHBr + 2Br and CHBr + Br 2 , all with release of more energy into translational degrees of freedom, could be responsible for the broad continuum absorption. The ionization potential of bromoform is 10.47 eV, , and some contribution of dissociative photoionization channels to the absorption spectrum is also expected at energies above 10.5 eV. 3 Action spectrum (solid line) of the CH(A) signal was taken with an interference filter in the 10−20 eV excitation energy range.…”
Single photon dissociation of bromoform using synchrotron radiation has been investigated by Fourier transform visible fluorescence spectroscopy (FTVIS). The photodissociation of bromoform in the 12-18 eV energy range results in several products, among which are the CH(A2Delta) and CH(B2Sigma) radicals. Vibrational and rotational state distributions of the CH(A2Delta) are determined from their fluorescence spectra. From the threshold photon energy above which emission from the CH(A2Delta) radicals is observed, the most likely process leading to CH(A) formation is CHBr3 --> CH + 3Br rather than CHBr3 --> CH + Br + Br2. The rotational Boltzmann temperatures in the CH(A --> X) emission spectra for v' = 0 and v' = 1 range between 1570 and 3650 K, depending on the excitation photon energy. From the high rotational excitation, the results suggest that the mechanism for the loss of three bromine atoms is most likely sequential. A small negative emission anisotropy of the CH(A) radicals [(Ipar - Iper)/(Ipar + 2Iper) = -0.024 +/- 0.005] is constant across the action spectrum; a small net absorption dipole of CHBr3 in the vacuum ultraviolet is parallel to the 3-fold symmetry axis of the CHBr3 molecule. The state distributions of the CH(A2Delta) radicals from multiphoton dissociation of bromoform using the 266 nm output (three photons) of a femtosecond laser (Boltzmann temperatures: T(v'=0)(rot)= 4250 +/- 300 K; T(v'=1)(rot)= 3100 +/- 550 K) are compared to those from the single photon dissociation results (Boltzmann temperatures: T(v'=0)(rot)= 3650 +/- 150 K; T(v'=1)(rot)= 2400 +/- 200 K) at the same total excitation energy under collision free conditions. The analysis of the CH(A) rotational populations shows hotter rotational populations for the femtosecond experiment, also suggesting sequential dissociation of the bromoform in the femtosecond experiment. The duration of the femtosecond laser pulse is approximately 180 fs, setting a limit on the time scales for the multiple dissociations.
“…Such multiple bonding should be reflected as bond shortening, whereas in SbC13 and BiCl3, the chlorine resonances with the more positive values of (dv dT), are those corresponding to chlorine atoms having the longest intramolecular bonds. Furthermore, the photoelectron spectrum of SbC13 suggests that such a back-bonding is not important (58). This mechanism is apparently not responsible for the effects observed in the Group V trichlorides.…”
Section: Iiechanisms For the Effects Of Taatermociecuhas Bondingmentioning
GRANT CALLUM GILLIES and RICHARD YULIAN CHALLIS BROWN. Can. J. Chem. 54,2266Chem. 54, (1976.Nuclear quadrupole resonance frequencies for the metal and chlorine atoms in AsC13 and SbCI; have been measured as functions of temperature and pressure. These data are analysed to obtain the isothermal volume dependences and the isochoric temperature dependences of the field gradient parameters. Existing Icnowledge of the Group V trichlorides shows that the strength of intermolecular bonding increases in the order AsC1, < SbCl; < BiC13, and this trend is reflected in the relative importance of volume effects in determining the nqr freq~lencies in these solids. A simple theory of the pressure dependences of nqr frequencies in molecular crystals is proposed, which accounts for all data presentiy available. The pressure coefficient contains static and dynamic contributions which are of opposite signs; the static contributioil is negative and becomes nulnerically larger as the strength of intermolecular bonding increases.GRANT C A L L U~~ GILL~LS et RICHARD JULIAN CHALLIS BROWN. Can. J. Chem. 518, 2266Chem. 518, (1976. On a mesure les frequences de resonance iluclCaire quadrupolaire des atomes mCtalliques et des chlores dans le AsC1; et le SbC13 en fonction de la temperature et de la pression. On a analysC ces donnCes pour obtenir des dCpendances volumiques isothermes et les dipendances isochore de tempkrature pour les paramiitres de gradient de champ. I e s connaissances existantes des trichlorures du groupe V montrent que la force des liaisons intermolCculaires augmente dans l'ordre AsCi, < SbC13 < BiC13; cette tendance se refliite dans l'importance relative des effets volumiques lors de la determination des frCquellces rilq de ces solides. On propose une thCorie simple pour expliquer la dependance entre la pression et les frkquences rnq des cristaux molCculaires; cette theorie tient compte de toutes les doililCes qui existent presentement. Ees coefficients de pression contiennent des contributions statiques et dynamiques qu.i son? de signes opposCs. La contribution statique est negative et devient numeriquement plus grande 2 mesure que la force de liaison intermolCculaii-e augmente.[Traduit par le journal]
“…The energy level ordering predicted from approximate MO calculations disagrees with the experimentally determined ordering. Nicholson and Rademacher (117) studied the PE spectra of Sb III halides. Their results indicated that (p-d)x back-donation is probably not important in these compounds.…”
Section: Baker Et Al (93) Correlated the Dihedral Angle In Me2s2mentioning
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
