1 / 16

CF3Br agust,www,....cf3br/PPT-081210ak agust,heima,....Sept10/XLS-081210ak.xls

CF3Br agust,www,....cf3br/PPT-081210ak.ppt agust,heima,....Sept10/XLS-081210ak.xls agust, heima,...PXP-291110ks/Leiðrétt-291110ks-081210ak.pxp (CF3+) agust,heima,... PXP-291110ks/Br 1D-REMPImW-291110ks-081210ak.pxp (Br+). Bond dissociation for CF 3 Br revisited:

Download Presentation

CF3Br agust,www,....cf3br/PPT-081210ak agust,heima,....Sept10/XLS-081210ak.xls

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. CF3Br agust,www,....cf3br/PPT-081210ak.ppt agust,heima,....Sept10/XLS-081210ak.xls agust, heima,...PXP-291110ks/Leiðrétt-291110ks-081210ak.pxp (CF3+) agust,heima,... PXP-291110ks/Br 1D-REMPImW-291110ks-081210ak.pxp (Br+)

  2. Bond dissociation for CF3Br revisited: The value used in http://notendur.hi.is/agust/rannsoknir/rempi/cf3br/PPT-090910ak.ppt (25 986.80 cm-1)is based on a paper from 1966 (see slide 3 in http://notendur.hi.is/agust/rannsoknir/rempi/cf3br/PPT-090910ak.ppt) The value used by Suto and Lee (JCP, 79(3), 1127, (´83) (see: http://notendur.hi.is/agust/rannsoknir/papers/jcp79-1127-83.pdf page 1131), based on Thermochemical data (Okabe, “Photochemistry of small molecules”, (1978)) is 2.98 eV (*8065.54093 cm-1/eV) = 24035.31 cm-1 which is is significantly lower. CF3+ + Br- threshold revisited: This affects the estimate of the CF3+ + Br- threshold: E(CF3+ + Br-) = 24035.31 + 72912.48 - 27129.17 = 69818.62197 cm-1 agust,heima,....Sept10/XLS-081210ak.xls

  3. CF3* + Br thresholds: Suto and Lee (JCP, 79(3), 1127, (´83) (see: http://notendur.hi.is/agust/rannsoknir/papers/jcp79-1127-83.pdf page 1132): UV spectrum: 6.38 + 2.98 eV =.... 75493.46 cm-1 Vis spectrum: 6.36 + 2.98 eV = ....75332.15 cm-1

  4. UV spectrum: 75493.46 cm-1 Vis spectrum: 75332.15 cm-1 CF3* + Br thresholds agust, heima,...PXP-291110ks/Leiðrétt-291110ks-081210ak.pxp

  5. CF3* + Br thresholds UV spectrum: 75493.46 cm-1 Vis spectrum: 75332.15 cm-1 agust,heima,... PXP-291110ks/Br 1D-REMPImW-291110ks-081210ak.pxp

  6. Now let´s look at the energetics with respect to CF3+ formation via CF3* formation (see fig. Next slide)

  7. (Semi) schematic energy figure: E/cm -1 CF3 + + Br 96947.79 cm-1 CF3Br+ + e- 91980 cm-1 CF3 * + Br 80 000 cm-1 75493.46/75332.15 cm-1 CF3 + + Br- 69818.62 cm-1 {CF3+Br-}? Ion-pair state? ca. 24035.31 cm-1 CF3 + Br CF3Br(?) R(CF3 –Br) Agust,heima,...CF3Br/Sept10/PXP-081210ak.pxp; Layout::0, Graph: 0, Table::0

  8. Possible dissociation mechanism(1): Ry -> Ion-pair -> CF3+ + Br- formation E/cm -1 CF3 + + Br 96947.79 cm-1 CF3Br+ + e- 91980 cm-1 (1) CF3 * + Br 80 000 cm-1 CF3 + + Br- 75493.46/75332.15 cm-1 CF3 + + Br- 69818.62 cm-1 {CF3+Br-}? Ion-pair state? ca. 24035.31 cm-1 CF3 + Br CF3Br(?) R(CF3 –Br) Agust,heima,...CF3Br/Sept10/PXP-081210ak.pxp; Layout::0, Graph: 0, Table::0

  9. Possible dissociation mechanism(2): Ry -> CF3* + Br dissociation E/cm -1 CF3 + + Br 96947.79 cm-1 CF3Br+ + e- 91980 cm-1 (2) CF3 * + Br 80 000 cm-1 75493.46/75332.15 cm-1 CF3 + + Br- 69818.62 cm-1 {CF3+Br-}? Ion-pair state? ca. 24035.31 cm-1 CF3 + Br CF3Br(?) R(CF3 –Br) Agust,heima,...CF3Br/Sept10/PXP-081210ak.pxp; Layout::0, Graph: 0, Table::0

  10. UV spectrum: 75493.46 cm-1 Vis spectrum: 75332.15 cm-1 • This brake in CF3+ intensity could be • because • -for 2hv < 75332 cm-1 only channels • occurs (i.e. CF3Br** ->-> CF3+ + Br-) • b) for hv > 75332 cm-1, competition • Between (1)(direct CF3+ formation) • and (2)(CF3* formation) • However based on PD data the observed • CF3+ signal all over most probably is • mainly due to (1) (i.e. direct CF3+ formation) CF3* + Br thresholds agust, heima,...PXP-291110ks/Leiðrétt-291110ks-081210ak.pxp

  11. Now let´s compare the “spin-orbit splitting” structure observed in the fluorescenec Spectrum for CF3Br and mentioned by Suto and Lee (JCP, 79(3), 1127, (´83) (see: http://notendur.hi.is/agust/rannsoknir/papers/jcp79-1127-83.pdf page 1132), i.e.

  12. Fluorescence maxima (b) (c) (a) (d) agust, heima,...PXP-291110ks/Leiðrétt-291110ks-081210ak.pxp

  13. The fluorescenec maxima do not match CF3+ signal maxima. On the contrary It looks more as if the maxima are in between peaks or close to minima in CF3+ signals (peaks (a)- (c). This could further indicate that there is a competition between channels (1) and (2)! http://notendur.hi.is/agust/rannsoknir/papers/jcp101-2069-94.pdf : 2) 11.7 eV 1) 11.4 eV Try to search for systematic spacing between peaks close to 0.3 and 0.46 eV:

  14. Now let´s look at quantum defects: 0.3 eV 0.46 eV 0.2 eV 0.35 eV 0.264 eV 1) En = 74546.9 cm-1 = 9.24 eV 2) En = 9.24+0.3 = 9.24 eV agust, heima,...PXP-291110ks/Leiðrétt-291110ks-081210ak.pxp

  15. = n – sqrt(R/(EI-En)); n = 5, R = 13.61 eV 1) d = 2.5 2) d = 2.5 Which is what one might expect for d for R-Br, p orbitals (and better value than that given by Eden et al. (http://notendur.hi.is/agust/rannsoknir/papers/cp323-313-06.pdf ) of 2.71) : See: http://notendur.hi.is/agust/rannsoknir/papers/jpcA112-7170-08.pdf (CH3Br) and http://notendur.hi.is/agust/rannsoknir/papers/CP148-315-90.pdf (Br2) Ergo: I conclude that the peaks at 1) just below 76000 cm-1 and 2) ca 78000 cm-1 are due to transitions to the Rydberg states: 1) [CF3Br+ (X 2E3/2)]c 5p and 2) [CF3Br+ (X 2E1/2)]c 5p Possibly the peak near 80500 cm-1 is due to transition to [CF3Br+ (A 2E1/2)]c 5p

  16. ...but what about the “peak” just below 77000 cm-1, i.e ca 1000 cm-1 above The peak for [CF3Br+ (X 2E3/2)]c 5p . Could that be a vibrational Band? NIST => ERGO: yes it could indeed be a vibrational band such as CF3 stretching(?)

More Related