1. (https://notendur.hi.is/agust/rannsoknir/rempi/ch3i/PPT-050112ak.ppt )
CH3I:
agust,www,...rempi/ch3i/PPT ak.ppt
( )
agust,heima,...REMPI/CH3I/PXP ak.pxp
(energetics and abs. spectrum)
(energetics)
Content: pages:
compound: availability and physical properties….. 2-3
Absorption spectra on www………………………………. 4-14
Papers………………………………………………………………
Rydberg state peaks / spectra…………………………
VMI-REMPI exp. Plan (Ry. Peaks)……………………
Important papers (summary table)………………… 33-34
Energetics…………………………………………………….. …………
REMPI spectra and assignments from the literature:……………………………………
Comparison of absorption and REMPI spectra………………………………………… 48
High energy REMPI vs abs. spectra………… ………. 56,64-66
Exp. Progress vs. Dates……………………………
CH3I and CH3I+ (X´s) energetics, vibrational modes and energies………………………………………
CH3 and CH3+ energetics………………………
Updated:

2. Eiríks project
1) CH3I:
Svana´s , :

3. http://en.wikipedia.org/wiki/Methyl_iodide :
liquid
Vapor pressure:
CRC:
1 mm 10 40
100
400
760 mp S
-45.8oC
-24.2
-7.0
+25.3
42.4
-64.4
Vapor pressure = 100 Torr for -7 oC
See cooling baths:

11. ATH 1
ATH 2

12.
ATH 1
(2007)
agust,heima,...REMPI/CH3I/PXP ak.pxp; Lay:0, Gr:0

13. ATH 1
agust,heima,...REMPI/CH3I/PXP ak.pxp; Lay:0, Gr:0

14.
ATH 2
agust,heima,...REMPI/CH3I/PXP aka.pxp; Lay:0, Gr:0

15. Absorption references:

16. Absorption references:

17. Absorption references:
See tables 4-7 in
The paper

18. no.: no.: (9) (2) (8) (11) (7) (3) (5) (6) (10)
no.:
(9)
no.:
(2)
(8)
(11)
(7)
(3)
(5)
(6)
(10)

19.
(1)

20.
(3)
(10)
(5)
(6)
no.:

21. VMI-REMPI experimental plan:
CH3I:
no.
2hv/ eV
2hv/cm-1
1hv/cm-1
l / nm(1hv)
Rydberg state
converging to
ref:
Comment 1
6.906
6s (1/2) +v2
2E1/2 $
Table 5*
Not accessable by MOPO; try dye laser 2
7.306
6p (0…) #
2E3/2
Table 4*
Try use MOPO 3
7.36
6p(3/2) +v3
Table 6 * 4
7.381
(?)
Unassigned peak, relatively strong (?) 5
7.402
6p(3/2) +nv6 6
7.642
6p(3/2) +nv1 7
7.82
5d(0,…) # 8
7.996
6p(0,…) # 9
8.022
7s(0,…) # 10
8.299
7s(3/2) +nv2
Table 6* 11
8.429
7p(0,…) # 12
8.652
i.e. 6 fundamental (0,…) bands (#); 5 vibrational bands; 1 uncertain band(?) / three bands for convergence to 2E1/2 ($)
*ref:
; see slides below(figs) and above (Tables)
; sheet: Ry spectra

22.
(1)
See slide 21 above

23. ? See slide 21 above (no.) (2) (3) (5) (6) (7) (8) (9) (10) (11) (4)
(no.)
(2)
(3)
(5)
(6)
(7)
(8)
(9)
(10)
(11) ?
See slide 21 above
(4)

24.
(12)
See slide 21 above

26. Check REMPI work
-by Donovan et al.
-references in CH3Br REMPI paper etc.
With repect to Rydberg state structure.

27. Papers: See also Eirik´s folder
Rydberg states:
RESONANCE-ENHANCED MULTIPHOTON IONIZATION PHOTOELECTRON- SPECTROSCOPY ON NANOSECOND AND PICOSECOND TIME SCALES OF RYDBERG STATES OF METHYL-IODIDE
Abstract: Rydberg states of methyl iodide have been investigated using resonance enhanced multiphoton ionization in combination with photoelectron spectroscopy with nanosecond and picosecond laser pulses. The study of the ns (6 less-than-or-equal-to n less-than-or-equal-to 10) Rydberg states in two-, three-, and four-photon excitations has resulted in an unambiguous identification of state [1] in the 7s and 8s Rydberg states. As a consequence, it is concluded that the transition to 6s[1] in two- and three-photon excitations is anomalously weak. The application of photoelectron spectroscopy to identify the electronic and vibrational nature of a resonance has led to a major reinterpretation of the excitation spectrum of the 6p Rydberg state in two-photon excitation. In many of the recorded photoelectron spectra anomalous electrons are observed, which derive from a one-photon ionization process. This process is suggested to find its origin in the mixing of 6p and 7s character into higher-lying Rydberg states. The major difference between resonance enhanced multiphoton ionization photoelectron spectroscopy with nanosecond and picosecond lasers is found in a less effective dissociation of the molecule in the picosecond experiments.
...Ry states, state mixing, vibr. Freq. Modes, (2+1)REMPI spectra and assignments
of Rydb. states

28.
(2+1)REMPI..3p Ry

29. https://notendur. hi. is/agust/rannsoknir/papers/CH3X/CH3I/jpc86-60-82
Shows 1) mass spectra and 2) energetics

30.
Bond energies, ..

31. Less useful but new papers:1)
Isotopic effect in the (2+1) REMPI spectra of (13)C-substituted methyl iodide for UV selective dissociation
To investigate a possible means of achieving isotopic enrichment of methyl iodide (CH(3)I), we studied the 6s Rydberg states of (13,12)CH(3)I by (2+1) resonance-enhanced multiphoton ionization. For 3; 3(1)(0) band (v3 hot band) excitation ( at a full width at half maximum of 14 cm (1)), we observed a well-resolved isotope shift of +16 cm (1). The band shape, which has a broad shoulder on the red side and an abrupt decrease on the blue side, indicates that this resonance is ideal for enriching the concentration of the desired lighter isotope (the isotopomer). (C) 2011 Elsevier B.V. All rights reserved. 2)
Photoelectron imaging of 8p Rydberg states of atomic iodine following methyl iodide A-band decomposition
Photoelectron imaging technique has been applied to study (2 + 1) REMPI of atomic iodine through 8p Rydberg states around 253 nm. Full three-dimensional state-specific speed and angular distributions of the photoelectrons were recorded. The branching ratios among the different I(+) levels revealed that the perturbation on ((3)P(2))8p series is particularly large among the ((3)P(2))np series. The violation of core-conserving ionization is attributed to the interactions between the ((3)P(2))8p and ((1)D(2))6p series. The photoelectron angular distributions were found to be well characterized by P(2)(cos theta) and P(4)(cos theta). A relatively high positive beta(2) and a relatively low beta(4) observed in (2 + 1) REMPI process indicated that the ionization process can be approximately considered as single-photon ionization via the weakly aligned ((3)P(2))8P intermediate states. (C) 2009 Elsevier Inc. All rights reserved.

32. https://notendur. hi. is/agust/rannsoknir/papers/CH3X/CH3I/jams2-93-11

33. URLs: Authors; Titles Important papers:
S. Eden,*,1, P. Lima˜o-Vieira ,2, S.V. Hoffmann , N.J. Mason; VUV spectroscopy of CH3Cl and CH3I
R. Locht ,*, B. Leyh, H.W. Jochims , H. Baumgärtel; Medium and high resolution vacuum UV photoabsorption spectroscopy of methyl iodide (CH3I) and its deuterated isotopomers CD3I and CH2DI. A Rydberg series analysis
M. R. Dobber, W. J. Buma, and C. A. de Lange ; Resonance enhanced multiphoton ionization photoelectron spectroscopy on nanosecond and picosecond time scales of Rydberg states of methyl iodide ; REMPI
David W. CHANDLER, John W. THOMAN Jr. , Maurice H.M. JANSSEN, David H. PARKER ; PHOTOFRAGMENT IMAGING: THE 246 nm PHOTODISSOCL4TION OF CHXI
Steven P. Sapers and D.J. Donaldson; A REMPI investigation of methyl iodide Rydberg state predissociation
D. H. Parker and R. B. Bernsteln; Multlphoton Ionization-Fragmentation Patterns of Alkyl Iodides
Juan Chen et al.; VUV photoionization of (CH3I)n (n = 1-4) molecules.
Atsushi Wakai et al.; Isotopic effect in the (2+1) REMPI spectra of 13C-substituted methyl iodide for UV selective dissociation
Huan Shen et al.; Photoelectron imaging of 8p Rydberg states of atomic iodine following methyl iodide A-band decomposition
Debra Jo Scardino et al.; The multiphoton ionization spectrum of methyl iodide revisted: 1.67–2.2 eV excitation
Ian J. McNaught; Structural Parameters of Methyl Iodide by Infrared Spectroscopy
Zhiyuan Min, T. Ridley, K.P. Lawley *, R.J. Donovan; Two-colour bound-free-bound spectroscopy of the [2E1/2]c6S Rydberg states of CHgI and CD3I
.. T. Ridley, K. P. Lawley* and R. J. Donovan; Ionic and Rydberg states of studied by high resolution CF3 I photoelectron (ZEKE-PFI) and resonance-enhanced multiphoton ionisation spectroscopy

34. URLs:
Authors; Titles
L. Rubio-Lago et al.; The photodissociation of CH3I in the red edge of the A-band: Comparison between slice imaging experiments and multisurface wave packet calculations
Young-Jae Jung et al.; Photoelectron imaging spectroscopy for „211… resonance-enhanced multiphoton ionization of atomic iodine produced from A-band photolysis of CH3I
W.C. Price; The Far Ultraviolet Absorption Spectra and Ionization Potentials of the Alkyl Halides. Part I
S. FELPS, P. KOCHMANN, P. BRINT, AND S. P. MCGLYNN ; Molecular Rydberg Transitions The Lowest-Energy Rydberg Transitions of s-Type in CH3X and CD3X, X = Cl, Br, and I L 2
N. Thire´, ab R. Cireasa,ab D. Staedter,ab V. Blanchet*ab and S. T. Prattc; Time-resolved predissociation of the vibrationless level of the B state of CH3I
M. G. González, J. D. Rodríguez, L. Rubio-Lago, and L. Bañaresa); Communication: First observation of ground state I(2P3/2) atoms from the CH3I photodissociation in the B-band
M. G. Gonza´lez,a J. D. Rodrı´guez,a L. Rubio-Lago,a A. Garcı´a-Velab and L. Ban˜ares*a; Slice imaging and wave packet study of the photodissociation of CH3I in the blue edge of the A-band: evidence of reverse 3 Q0 ’ 1 Q1 non-adiabatic dynamics
L. Rubio-Lago,ab J. D. Rodrı´guez,a A. Garcı´a-Vela,c M. G. Gonza´lez,a G. A. Amarala and L. Ban˜ares*a; A slice imaging and multisurface wave packet study of the photodissociation of CH3I at 304 nm
Sonia Marggi Poullain,a Marta G. González,a Peter C. Samartzis, b Theofanis N. Kitsopoulos,b,c Luis Rubio-Lagoa and Luis Bañaresa∗ ; New insights in the photodissociation of methyl iodide at 193 nm: Stereodynamics and product branching ratios
Andreas Kartakoullis,†,‡ Peter C. Samartzis,† and Theofanis N. Kitsopoulos*,†,‡; Photodissociation of Methyl Iodide and Methyl Iodide Clusters at 193 nm
A velocity map imaging study of the photodissociation of the methyl iodide cation
Bailin Zhang, Jinghui Zhang, and Kopin Liu; Imaging the “missing” bands in the resonance-enhanced multiphoton ionization detection of methyl radical
Jeffrey W. Hudgens, T. G. DiGiuseppe, and M. C. Lin; Two photon resonance enhanced multiphoton ionization spectroscopy and state assignments of the methyl radical

35. Now we need to look at the energetics, analogous to that for CH2Br2:
(See slides 6 -11)

36.
Fig 10:

37. NIST
IE:
cm-1

38.
cm-1

39. CH3:

40. CH3I D:
2.38 eV
cm-1
Factors:
f1:
8.36E+01
cm-1 / (kJ mol-1)
f2:
3.50E+02
cm-1 / (kcal mol-1)
f3:
cm-1/eV
E(6s) =
E(4P;5s)+D=
IE(CH3I)=
9.54
NIST
IE(I)=
E(S/O;I)=
E(CH3+I*(1/2))=
E(CH3+I+ + e)=
IE(CH3) =
9.84
 NIST
E(CH3+ + e + I)
EA(I) =
E(CH3+ + I-)=
E(I+)-E(I*)=

41. cm-1 CH3I+ + e; 76945.26047 CH3I CH3 + I+ + e; 103491.0874
CH3+ + e + I;
CH3I+ + e;
CH3 + I**(min);
CH3 + I*;
CH3 + I;
CH3I

42. Abs. spectrum CH3I+ + e; 76945.26047 CH3I (n) = number of photons (4)
CH3+ + e + I;
Abs. spectrum
(3)
CH3I+ + e;
CH3 + I**(min);
70000
(2)
55000
(1)
CH3 + I*;
CH3 + I;
CH3I

43. 70000 cm-1 CH3+ + e + I; 65707.27 cm-1 ..threshold hv(Laser)=16426.82
CH3 + I+ + e;
cm-1
..threshold: hv(Laser) = ( nm)
CH3+ + e + I;
cm-1
..threshold hv(Laser)=
( nm)

44. REMPI spectra and assignments
from the literature:

45. n = number of resonance excitation photons n: 2
n = number of resonance excitation
photons
s -States and spectra
observed in
Two-photon REMPI

46. n: 2
s -States and spectra
observed in
Two-photon REMPI

47. n: 2
s -States and spectra
observed in
Two-photon REMPI

48. 2hv : p -States and spectra observed in Two-photon REMPI 58000 64000
58000
64000
2hv :
p -States and spectra
observed in
Two-photon REMPI

49. Comparison of absorption and REMPI spectra
Abs. Spectrum:
Comparison of absorption
and REMPI spectra :
REMPI spectrum:
2hv(cm-1/
eV)
58000/
7.191
60000/
7.439
62000/
7.687
64000/
7.935

50. s states spectra Ca. Spectral observed region for in (2+n)
REMPI
Ca. Spectral
region for
R590!
p states spectra
observed
in (2+n)
REMPI

51. s states spectra observed in (2+n) REMPI p states spectra observed
64000
p states
spectra
observed
in (2+n)
REMPI
58000

52. Comparison of absorption and REMPI spectra:
p states
spectra
observed
in (2+n)
REMPI
Comparison of absorption and REMPI spectra:
64000
62000
60000
58000

53. 72900
72500

55. Abs. spectrum CH3I+ + e; 76945.26047 CH3I (n) = number of photons (4)
CH3+ + e + I;
Abs. spectrum
(3)
CH3I+ + e;
CH3 + I**(min);
70000
(2)
55000
The A-band
x100
(1)
CH3 + I*;
CH3 + I;
CH3I

56. CH3I+ + e; 76945.26047 Abs. spectrum The A-band n s*(C-I) x100
(n) = number of photons
CH3I+ + e;
70000
cm-1
(2)
Abs. spectrum
cm-1)
55000
The A-band
n s*(C-I)
x100
(1)

57. Absorption spectrum CH3+ 1D REMPI uncorrected 2hv

58. ??? cm-1
pnt

59. IDEA!: an I2+ mass peak observed could be due to a molecular dimer
(CH3I)2
ERGO: let´s see the effect of less cooling, i.e.
less % argon
2) less backing pressure
. Let´s check the literature
Literature:
: Van der Waals complexes
: “Ground electronic state I2 is formed from the photolysis of methyl iodide dimers”
Sjá meira neðar
See example for effect of buffer gas (rare gas) on jet cooling next slide:

60. http://www.nature.com/nphys/journal/v4/n8/box/nphys1031_BX1.html :
Small molecular density=
molecular diffusion
Largest molecular density=
molecular beam
Skimmer;
Not used in our case
Beam axis
medium molecular density

61. https://notendur.hi.is/agust/rannsoknir/papers/CH3X/CH3I/jppbA100-9-96.pdf :

62. https://notendur.hi.is/agust/rannsoknir/papers/CH3X/CH3I/jpc100-11559-96.pdf :
& :

63. Ln(p) ln(p) vs 1/T is nonlinear suggesting less importance of
1 mm 10 40
100
400
760 P
Torr S
-45.8
-24.2 -7
25.3
42.4
t/oC
227.35
248.95
266.15
298.45
315.55
T/K
1/T (K-1)
ln(p)
Ln(p)
ln(p) vs 1/T is
nonlinear suggesting
less importance of
dimers as
temperature rizes.
1/T (K-1)

64. This could mean that CH3I dimers are even formed in the vapour above the trap
when cooled with CCl4 slash bath (-23oC)!!
--further suggesting that it might be better to use less cooling for the trap:
How about to use cold water only (analogous to that used for CH2Br2
earlier) ???

65. No clear correspondance between REMPI
and absorption spectra in this region
Absorption
spectrum
CH3+ 1D REMPI
uncorrected
2hv

66. What on earth is that??? CH3+ 1D REMPI uncorrected Absorption spectrum
2hv

67. This looks like P, Q and R brances Of symmetric top: seen next slide
CH3+ 1D REMPI
uncorrected
Absorption
spectrum
D =
2hv

68. IR róf topsamhverfra sameinda /
IR spectra for symmetric top molecules:
CH3I:
B: Fundamentals of Molecular Spectroscopy  eftir
C.N. Banwell og E.M. McCash, (McGraw-Hill, 4. útg. 1994)

70. Are these all iodine atomic lines? What transitions are these, Eiríkur?
hv(laser)

71. Same molecular peak seen in the I+ and CH3+ spectra
Small but
significant
peak
C atomic lines
hv(laser)

72. CH3+ REMPI
cm-1 og
ftp:// /Data/CH3I/Calibartion Work/calibration/ allt I cal, 16220_17510 funky17540_ pxp

73. CH3+ REMPI
cm-1
8.408
8.4
cm-1 og
ftp:// /Data/CH3I/Calibartion Work/calibration/ allt I cal, 16220_17510 funky17540_ pxp

74. I+ REMPI og
ftp:// /Data/CH3I/Calibartion Work/calibration/ allt I cal, 16220_17510 funky17540_ pxp

75. Symmetric top:

76. 69852.92828 cm-1 OUR CH3+ REMPI spectrum At 69852.9 is Due to CH3 !!!!
OUR CH3+ REMPI spectrum
At is
Due to CH3 !!!!
Check this reference

77. https://notendur.hi.is/agust/rannsoknir/papers/CH3X/CH3I/jcp89-3986-88.pdf :

78. https://notendur.hi.is/agust/rannsoknir/papers/CH3X/CH3I/jcp89-3986-88.pdf :
cm-1
Ours
NB!:
DK = 0

79. Coupling terms Excited state NB!: DK = 0 Ground state:
Coupling terms
Excited state
NB!:
DK = 0
Ground state

80. ..but what about this spectrum:
cm-1
cm-1
It must be because of CH3
There is no reported electronic state for CH3 at this wavenumber
The spacing of cm-1 between the two CH3+ spectra suggests that it could be
A vibrationally excited state

81. Let´s check references
Could be the
a2 n2 (OPLA)
vibrational mode
Let´s check references
out‐of‐plane large amplitude
(OPLA)-mode
= umbrella modes

82. ...but these seem, generally to be the lowest numbers
NB!: OPLA modes can be significantly different for excitede states than for
The ground state, thus:
NIST:
...but these seem, generally to be the lowest numbers

83. Our spectrum simulated for parameters in:
Calculations were performed in
cm-1 P Q R S O

84. cm-1
Since the Q branch in the cm-1
system is degraded to red (low wavenumber)
opposide of what is found for the cm-1
system (slide 72) it suggest that
B´< B´´ opposide of what is found for the
cm-1 sysem (see slide 68) where
B´= 9.90 cm-1 and B” = cm-1
First attempts to simulate the vibrationally excited band of CH3:

85. cm-1
= B”
=DN”
=DNK”
=B´
=DN´
=DNK´
“=n0
=DC
=DDK
DK = 0 Q P R O S

86. date
Exp. work
Nm (pred/exp.)
Comments/ref.
18.9 Mo
NOT
19.9
Tue
CH3I (2) (CH3+,PES) /
MOBO, File: (and partly)
20.9 We
CH3I(1)
(CH3+,CH2+,I+,PES) /
MOBO power fell down; switched to Exc./dye File: , partly
21.9
Thu
CH3I(12) (CH3+)
(dye l)/ (pred.)/ (exp.)
Exc./dye, (Rhodamin 6G in MeOH); NB: polarizer was not inserted; ERGO: the angular distrib. Is invalid. File:
22.9
Fri
CH3I(12) (CH3+, I+, PES)
(dye l)/ (pred.)/ (exp.)
Exc./dye, (Rhodamin 6G in MeOH); polarizer IN; CH2+ signal too week.
Calibration for ion images changed from eV = e-5 x (pix)2 (used ) TO eV = 3.50e-5 x (pix)2 (to be used from now)
23.9 Sa
Psiloritis, 19 km. hot
24.9 Su
25.9
CH3I(11) (CH3+, I+, PES)
(dye l)/ (pred.)/ (exp.)
Exc./dye, (Rhodamin 6G in MeOH);
Abel conversion performed for CH3+ images (CH3+ signal week)
26.9
CH3I(ca.12)CH3+, I+ and PES
573.2(dye l.)/
------/ 286.6(exp.)
Off resonance signals near Ry(12)
27.9
NO experiment: problem with circulator; however good signal for Ry(1)
28.9
CH3I (1) and off res.: (CH3+,I+,PES)
Exc./dye, (DMQ in dioxine)
29.9
CH3I (2) (CH3+,CH2+,I+,PES) /
To top

87. Sternes = Koudouma (46 km) 1.10 Su Work at home; CH32I & CH3Br 2.10 Mo
To top
date
Exp. work
nm /predicted and used
Comments/ref:
30.9 Sa
Sternes = Koudouma (46 km)
1.10 Su
Work at home; CH32I & CH3Br
2.10 Mo
CH3I(3): CH3+, CH2+, I+, PES
(exp.)/ (pred.?)
Lot of rings!
3.10 Tu
CH3I(4a):CH3+,I+,PES & CH3I(4b):CH3+
(exp.) & (exp.)
4.10 We
CH3I(4b): I+ & CH3I(4c):CH3+,I+,PES (?)
(exp.)& (exp)(?)
Something strange about the data storaging for (4c)
5.10 Th
CH3I(7): CH3+,I+,PES
(dye l.)/ (pred.)/ (exp.)
Lot of rings in PES due to I** +hv -> I++e
6.10 Fr
CH3I(8): CH3+, I+, PES
(dye l.)/ (pred.)/ (exp.)
PG fiddled with the PES calibration and came to the conclusion that f = 3.20e-5 (or even lower) is more appropriate than 3.29e-5
7.10
Gorge north of Zaros (15.51.km)
8.10
„Keilir“ =Amodara (28.79 km)
9.10
Checked Ry(8) for space charging
(dye l.)/ (pred.)/
Leak in excimer laser; Found evidences for space charging effects
10.10
CH3I(6): CH3+, I+, PES CH3I(9): I+, PES(?)
(6): (dye l.) / (pred.)/
317.12(exp.); (9): (dye l.)/ (pred.)/ (exp.)
PG: PES for (9) is strange ( )
(9) Too week signal to record CH3+

88. To top
date
Exp. work
nm predicted and used
Comments/ref:
11.10. We
(9): PES 2) CH3+,I+,PES
3) (6): PES
618.22(dye l.) 2) (dye l.)(?)
3) (dye l.)
Checked Ry(9) again; no major change from yesterday; still stange behavious; moved to Ry(6) to see if that is reproducable; tested space charge effect
12.10. Th
(3): CH3 2) (2): CH3
1) (dye l.) 2) (dye l.)
Checked (2) and (3) for space charge effects; less space charging observed for adiluted sample by higher laser power! Look at PG PPT file
13.10 Fr
Ath Costas 9:30(?)..CF arrives tonight.
14.10 Sa
Ólöf arrives in the evening

89. CH3I(X) energetics: :

90. CH3I+(X) energetics: :

91. CH3I+(X) energetics: :

92. X(CH3): Methyl Radical, CH3 Vibrational states of the ground
To top
X(CH3):
Methyl
Radical, CH3
Vibrational states
of the ground
electronic state

93. *3 *2 * CH3** *6 *5 *4 Methyl Radical, CH3 electronic state To top

94. http://webbook. nist. gov/cgi/cbook. cgi
X(CH3+):