CH2Br2:
1) Absorption
2) REMPI scans: overview (slides 12-15)
3) C+ REMPI vs absorption spectrum
agust,www,....ch2br2/PPT-010311ak.ppt
agust,heima,...CH2Br2/PXP-010311ak.pxp
agust,heima,...CH2Br2/PXP-020311ak.pxp
agust,heima,...CH2Br2/PXP-050311ak.pxp
agust,heima,...CH2Br2/C REMPI-130411jl.pxp
Searched for “CH2Br2 absorption” in Google:
Structure
Author(Year)
Temperature
Wavelength range
Information
CH2Br2
CausleyRussell(1975)
298K
110-180nm(0.25,0.5,1nm)
Details | Data
80
x10
-18
60
40
20
110
120
130
140
150
160
170
nm
180
Details
Structure:
CH2Br2
Name:
dibromomethane
Author(Year):
CausleyRussell(1975)
Temperature:
298K
Wavelength range: 110-180nm(0.25,0.5,1nm)
Bibliography:
G.C. Causley and B.R. Russell, "Vacuum ultraviolet absorption spectra of the
bromomethanes," J. Chem. Phys. 62, 848-857 (1975).
http://www3.hi.is/~agust/rannsoknir/papers/jcp062-848-75.pdf
Comments:
Extinction coefficients read at 0.25-, 0.5, and 1-nm intervals from Fig. 6 and converted to
absorption cross sections (conversion factor 3.8235x10-21).
Grein pöntuð (sjá slide 8) 020311:
G.C. Causley and B.R. Russell, "Vacuum ultraviolet absorption spectra of the bromomethanes," J. Chem. Phys. 62, 848-857 (1975).
Spectrum from paper and digitised spectrum from database superimposed:
80
x10
-18
60
40
20
110
120
130
140
150
160
170
180
Absorption
cross section
80
x10
-18
60
40
Ionization limit
83962.3 cm-1
20
60
65
70
75
x10
agust,heima,...CH2Br2/PXP-010311ak.pxp; Lay: 0, Gr:0
3
80
85
cm-1
90
Abs.
cross
section
Dye: C503
Predictions:
http://notendur.hi.is/agust/rannsoknir/rempi/cf3br/Bromine Lines-080910ks.doc
Br atomic
Lines
80
http://notendur.hi.is/agust/rannsoknir/papers/jpcA114-9991-10.pdf
Predictions:
C atomic
lines
Broken lines: from 2P1/2
solid lines: from 2P3/2
x10
-18
60
10.03.11m
09.03.11l
08.03.11k
40
07.03.11j
04.03.11a
03.03.11b
02.03.11c
01.03.11d
28.02.11e
25.02.11f
20
REMPI scans
for C503
70
05.03.11i
24.02.11g
Ionization limit
83962.3 cm-1
23.02.11h
75
80
x10
3
85
2hv/cm-1
See footnotes below:
agust,heima,...CH2Br2/PXP-020311ak.pxp ; Lay:1, Gr:1;
updated 130311
90
Dat for C503:
Footnotes:
m(100311):
ftp://130.208.167.52/Report/REMPI%20REPORT/20110310.html
l(090311):
ftp://130.208.167.52/Report/REMPI%20REPORT/20110309.html
k(080311):
ftp://130.208.167.52/Data/CH2Br2/20110308/readme.txt ; lot fo Br atomic lines
ftp://130.208.167.52/Report/REMPI%20REPORT/20110308.html ; Br atomic lines
j(070311):
ftp://130.208.167.52/Data/CH2Br2/20110307/readme.txt ;Br,H,CH,CH2 spectra in 82120-83028; Br atomic line in 82000-82140
ftp://130.208.167.52/Report/REMPI%20REPORT/20110307.html ; CH in 81760-81900
i(050311):
ftp://130.208.167.52/Report/REMPI%20REPORT/20110305.html ; 79500-79360 no good.
a (040311):
ftp://130.208.167.52/Data/CH2Br2/20110304/readme.txt & Clear C+ REMPI spectrum
ftp://130.208.167.52/Report/REMPI%20REPORT/20110304.html
b(030311):
ftp://130.208.167.52/Data/CH2Br2/20110303/readme.txt ; Br atomic lines observed
ftp://130.208.167.52/Report/REMPI%20REPORT/20110303.html
c( 020311):
ftp://130.208.167.52/Report/REMPI%20REPORT/20110302.html
d(010311):
ftp://130.208.167.52/Data/CH2Br2/20110301/readme.txt : NO mention about observation of C atomic lines(?)
ftp://130.208.167.52/Report/REMPI%20REPORT/20110301.html
e( 280211):
ftp://130.208.167.52/Data/CH2Br2/20110228/readme.txt ; strong Br atomic line seen
f(250211):
ftp://130.208.167.52/Data/CH2Br2/20110225/readme.txt : C atomic line seen; Br atomic line seen
ftp://130.208.167.52/Report/REMPI%20REPORT/20110225.html
g(240211):
ftp://130.208.167.52/Data/CH2Br2/20110224/Readme.txt
ftp://130.208.167.52/Report/REMPI%20REPORT/20110224.html
h(230211):
ftp://130.208.167.52/Data/CH2Br2/20110223/Readme.txt
ftp://130.208.167.52/Report/REMPI%20REPORT/20110223.html
Abs.
cross
section
Dye: C503
Predictions:
http://notendur.hi.is/agust/rannsoknir/rempi/cf3br/Bromine Lines-080910ks.doc
http://notendur.hi.is/agust/rannsoknir/papers/jpcA114-9991-10.pdf
Predictions:
C atomic
lines
80
x10
-18
60
Br atomic
Lines
Broken lines: from 2P1/2
solid lines: from 2P3/2
Dye:
R540
Group of
C atomic
lines
40
Ionization limit
83962.3 cm-1
Weak signals
20
18.03.11e
17.03.11d
16.03.11c
15.03.11b
14.03.11a
Weak signals
Horisontal lines: REMPI scans (see also slide above)
70
75
80
x10
3
85
2hv/cm-1
See footnotes below:
agust,heima,...CH2Br2/PXP-020311ak.pxp ; Lay:1, Gr:1;
updated 1970311
90
Footnotes:
a(140311; dye:R540):
ftp://130.208.167.52/Report/REMPI%20REPORT/20110314.html
b(15.03.11; dye:R540):
ftp://130.208.167.52/Report/REMPI%20REPORT/20110315.html
c(16.03.11; dye:R540):
ftp://130.208.167.52/Report/REMPI%20REPORT/20110316.html
d(17.03.11; dye:R540):
ftp://130.208.167.52/Report/REMPI%20REPORT/20110317.html
e(18.03.11; dye:R540):
ftp://130.208.167.52/Report/REMPI%20REPORT/20110318.html
Comment (020311):
• It will be interesting to see if there is a correlation between the CH2+, CH+, C+.
...spectra and the absorption spectrum shown above.
Have a look at this!:
Absorption
cross section Absorption
spectrum
Threshold for
C*(1D2) + 2hv -> C+ + e80625.27 cm-1
See: our CH3Br paper
Page 9994
G.C. Causley and B.R. Russell,
J. Chem. Phys. 62, 848-857 (1975).
7s(b1) d=3.01
x10
3
30
20
C+ REMPI spectra from
040311:
10
c20110_20145 to
c20170_20205
Peak at
80663 cm-1
0
76
78
80
x10
agust,heima,...CH2Br2/PXP-050311ak.pxp; lay:0; Gr:1
3
82
2hv/cm-1
84
Comments:
• The C+ REMPI peak fits exactly the absorption peak
for CH2Br2 corresponding to transition to the 7s(b1) Rydberg state according to
the paper by Causley and Russel (C&R)
(http://www3.hi.is/~agust/rannsoknir/papers/jcp062-848-75.pdf)
• I wonder if the Rydberg state assignment by C&R is correct(?). It is more likely that
a (2+n)REMPI spectrum is due to a resonance transition to a p-Rydberg state due
selection rules!
• Are peaks also found at this position (see above) for the CH2+ and CH+ ions?
• We desperatelly need “Dye power curves” along with the absorption spectrum
• Most likely C is formed after 2hv excitation to a Rydberg state by channels such as:
CH2Br2** -> 2HBr + C
OR
CH2Br2** -> H2 + C + Br2
NB!: If the former channel is occuring we might see HBr (2+n) REMPI! ERGO:
Look for HBr REMPI in the CH2Br2 data.
updated 060311
40
x10
3
30
20
10
0
72
74
76
78
3
x10
agust,heima,...CH2Br2/C REMPI-130411jl.pxp
80
82