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Relative ion signals in CH3Br mass spectra vs. Rydberg states

This presentation discusses the relative ion signals (I(M+)/I(CH3+)) in CH3Br mass spectra compared to Rydberg states. Background spectra have not been subtracted. The data shows the variation in ion signals as energy increases or decreases.

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Relative ion signals in CH3Br mass spectra vs. Rydberg states

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  1. CH3Br, 051109 Relative ion signals (I(M+)/I(CH3+)) vs Rydberg states agust ,www,....Nov09/PPT-051109ak.ppt agust,heima,...CH3Br-Overall +mass-041109km-051109ak.pxp agust,heima, ....XLS051109ak.xls NB: background spectra have not been subtracted in the mass spectra shown below

  2. CH3+ 2hv C+(partly due to impurities) CH3+ + Br-/ Threshold 76695 cm-1 Mw

  3. CH3+ C+(partly due to impurities) 2hv 79594 79195 78410 78393 CH3+ + Br-/ Threshold 76695 cm-1 77841 77165 76672 75887 75395 68882 68675 67275 66503 66022 Mw

  4. Br+ 2hv CBr+ 78410 See below 77841 77165 CH3+ + Br-/ Threshold 76695 cm-1 76672 75887 75395 68882 68675 67275 66503 66022 Mw

  5. NB: relative ion signals (I(M+)rel) above are I(M+)/I(CH3+) • I(CHn+)rel ; n = 2,1 and I(Br+)rel increase as energy increases from 66000cm-1 to • the CH3+ + Br- threshold (76695 cm-1) • I(CHn+)rel ; n = 2,1 and I(Br+)rel decrease as energy increases above 76695cm-1 • I(Br+)rel vanishes for energies above about 78400. • I(CBr+)rel stays almost constant for all energies, 66000 – 78400 after which it • vanishes. • Now lets check background signals vs Rydberg state signals:

  6. agust,heima,...CH3Br-Overall +mass-041109km-051109ak.pxp : Above Threshold: Br+ CBr+ Rydb. state 77841 CH3+ Background Near 77542.2

  7. agust,heima,...CH3Br-Overall +mass-041109km-051109ak.pxp : Above Threshold: Br+ CBr+ Rydb. state 77165 CH3+ Background Near 77542.2

  8. It actually looks as if I(Br+)rel, I(CBr+)rel and I(CHn+)rel; n = 2,1 are slighly stronger for the “background signal” compared to the “neighbour” (Rydberg + bgr)-signals. Lets check more bgr signals:

  9. agust,heima,...CH3Br-Overall +mass-041109km-051109ak.pxp : Way above Threshold: Br+ CBr+ Rydb. state 78410 Rydb. state 79594 CH3+ Background Near 79324

  10. Comparable I(M+) signals are seen for Rydberg (+bgr) • and background signals!

  11. Near threshold CH3+

  12. It actually looks as if I(Br+)rel, only are slighly stronger for the “background signal” compared to the “neighbour” (Rydberg + bgr)-signal. Now we need to go below threshold

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