Updated (p:15-16, refs. & p:50-51)

Updated 180922 (p:15-16, refs. & p:50-51)
CH3Br, VMI-REMPI, 2016: Content: (ca.) pages Plan according to application………………………………………………. 2-4 From T. Ridley´s paper, 2008 on CH3Br……………………………….. 5-6 Our paper, 2010 on CH3Br………………………………………………… Mass spectra vs. REMPI spectra………………………………………….. 14 I(M+)/I(CH3+) (M = CH, Br, CBr) vs CH3+ REMPI spectrum……… 15-16, 50 Important papers………………………………………………………………… 17-18 Peak positions vs. Spectra (T. Ridley & OURS)…………………… Mass vs. REMPI spectra………………………………………………………. 26 Comments concerning REMPI and Mass spectra………………… 27 CH3, CH3+, CH3Br, CH3Br+ vibrational and e-states …………… CH3-Br bond energies vs. literature……………………………………… Exp. Progress vs. dates……………………………………………… Check list for experimental progress and processing work…….. 38 Br and Br* detections / resonances, transitions…………………… 39-40 KER basic formulas……………………………………………………………… processing procedures (examples)………………………………………… CH3 detection…………………………………………………………………………. 46 Thresholds……………………………………………………………………………… scanning ranges vs. thresholds (semi-schematic)……………………. 51 Updated (p:15-16, refs. & p:50-51)

Application text/ plans etc.:
To top

https://notendur. hi. is/~agust/rannsoknir/papers/jpcA112-7170-08
(T. Ridley et al. CH3Br paper, 2008) To top

To top :

To top ; our CH3Br paper

https://notendur. hi. is/~agust/rannsoknir/papers/jpcA114-9991-10
; our CH3Br paper To top

Mass spectra vs. CH3 REMPI spectra:
Ref: agust, heima,..ritsmidar/CH3Br(II)/ CH3Br-II doc; Fig. 2

I(CH+)/I(CH3+) vs CH3+ REMPI spectrum
Ref: agust, heima,..ritsmidar/CH3Br(II)/ CH3Br-II doc; Fig. 3(a) & agust, heima,..ritsmidar/CH3Br(II)/Figs/Fig.3/CH3REMPI vhw ak.pxp; Lay2, Gr9 ; Lay2, Gr9

I(M+)/I(CH3+) (M = Br, CBr) vs CH3+ REMPI spectrum
Ref: agust, heima,..ritsmidar/CH3Br(II)/ CH3Br-II doc; fig. 3(b) & agust, heima,..ritsmidar/CH3Br(II)/Figs/Fig.3/CH3REMPI vhw ak.pxp; Lay3, Gr10 ; Lay3, Gr10

Information / Content:
Important papers: To top Papers Information / Content: T. Ridley et al.: REMPI spectra etc. A. Kvaran et al.: REMPI spectra, etc. T.N. Kitsopoulos et al. Photodissociation study of CH3Br in the first continuum I. Powis et al.; Photofragmentation of CH3Br in the red wing of the first continuum absorption band T.N. Kitsopoulos et al., Slice imaging of methyl bromide photofragmentation at 193 nm T.N. Kitsopoulos et al., Slice imaging: A new approach to ion imaging and velocity mapping Christelle Escure et al., Ab initio study of valence and Rydberg states of CH3Br Causley and Russell, Vacuum ultraviolet absorption spectra of the bromomethanes Y. Song et al., High-resolution energy-selected study of the reaction CH3X+ ->CH3+ + X: Accurate thermochemistry for the CH3X/CH3X+ (X=Br, I) system Xiaofeng Tang et al. Dissociation of internal energy-selected methyl bromide ion revealed from threshold photoelectron-photoion coincidence velocity imaging T.N. Kitsopoulos et al., Multiphoton dissociation dynamics of CH3Br V. Blanchet et al., Bailin Zhang, Jinghui Zhang, and Kopin Liu; Imaging the “missing” bands in the resonance-enhanced multiphoton ionization detection of methyl radical

Information / Content:
Important papers: To top Papers Information / Content: Jeffrey W. Hudgens, T. G. DiGiuseppe, and M. C. Lin; Two photon resonance enhanced multiphoton ionization spectroscopy and state assignments of the methyl radical Wayne P. Hess, David W. Chandler and John W. Thoman Jr.; Photofragment imaging: the 205nm photodissociation of CH3Br and CD3Br G.N.A. Van Veen, T. Baller and A.E. De Vries: Photofragmentation of CH3Br in the A band. M. Laura Lipciuc and Maurice H. M. Janssen; High-resolution slice imaging of quantum state-to-state photodissociation of methyl bromide Sonia Marggi Poullain, David V. Chicharro, Alexandre Zanchet, Marta G. González, Luis RubioLago, María L. Senent, Alberto García-Vela and Luis Bañares; Imaging the photodissociation dynamics of the methyl radical from the 3s and 3pz Rydberg states

n = 5 [3/2]np;w 6 7 2 w = n3 n2 n1 n3 n2 5 [1/2]np;w 6 2 2 n3 n2 4
Bands according to (T. Ridley et al. CH3Br paper, 2008) To top 66019 75686 75905 n = 5 [3/2]np;w 6 7 2 w = n3 n2 n1 n3 n2 5 [1/2]np;w 78370 6 79610 2 2 n3 n2 68461 68684 78225 72977 80640 80758 4 [3/2]nd;w 6 2 2 2 n3 n2 n1 4 [1/2]nd;w 5 72655 2 75418 78401 n3 n2 78193 80674 80881 REMPI spectra pxp; Gr:0; Lay:0

n = 5 [3/2]np;w 6 7 2 w = n3 n2 n1 n3 n2 5 [1/2]np;w 6 2 2 n3 n2
Bands according to our assignments To top 68882 77165 n = 5 [3/2]np;w 6 7 2 w = n3 n2 n1 n3 n2 5 [1/2]np;w 6 66503 67275 2 2 n3 n2 [3/2]nd;w 69947 4 6 2 2 2 n3 n2 n1 4 [1/2]nd;w 5 74249 2 n3 n2 76689 REMPI spectra pxp; Gr:0; Lay:0

One-color detection work / ion detection:
66019 75686 75905 68882 77165 n = 5 [3/2]np;w 6 7 2 w = n3 n2 n1 n3 n2 5 [1/2]np;w 78370 6 79610 66503 67275 2 2 n3 n2 68461 68684 78225 72977 80640 80758 4 [3/2]nd;w 69947 6 2 2 2 n3 n2 n1 4 [1/2]nd;w 5 72655 74249 2 75418 78401 n3 n2 78193 80674 80881 76689 REMPI spectra pxp; Gr:0; Lay:0

Two-color detection work:

One-color detection work / e- detection:

CH3+ REMPI spectra (1/2)6p w = 2 0 5d (3/2)6d w = 2 0 To top
REMPI spectra pxp; Gr:0; Lay:0

Mass spectra normalized with respect to the CH3+ peaks:
To top E / cm-1 CHn+ n=1,2,3 iBr+ (i=79,81) CiBr+(i=79,81) CH Br- 76822 cm-1 x 2.5 Intensity 13 15 Mw / amu 79 91 Mass vs. REMPI pxp; Gr:22, Lay:12

To top Comments: Relative contributions of fragment ions, other than CH3+ and CBr + (i.e. CHn+ (n = 1,2) and Br+ ), -increase as 2hn increases from cm-1 to the CH3+ + Br- threshold (76822 cm-1) -decreases sharply as 2hn increases from the CH3+ + Br- threshold (76822 cm-1) for unknown reasons. Spectral features close to the CH3+ + Br- threshold (76822 cm-1) are particularly broad, (see slides 14-16) suggesting that lifetimes shorten, hence that dissociation channels open up (?) It is of interest to see whether / how images of fragments (in general) vary with 2hn on both sides of the CH3+ + Br- threshold (76822 cm-1). An additional CH3+ formation channel corresponding to ion-pair formations (CH3+ + Br- ) might appear above the CH3+ + Br- threshold (76822 cm-1) A Br- formation channel corresponding to ion-pair formations (CH3+ + Br- ) might appear above the CH3+ + Br- threshold (76822 cm-1)

Methyl Radical, CH3 Vibrational states of the ground electronic state
To top Methyl Radical, CH3 Vibrational states of the ground electronic state

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

http://webbook. nist. gov/cgi/cbook. cgi
CH3+

To top CH3Br:

CH3Br+: To top

D0 DD0 CH3Br --> CH3 + Br 24585 176 23400 133 23741 669 25217 35 24728 140 Roux 24164 16 24306 195

To top Exp. Progress:

To top date Exp. work nm (MOBO scale) Comments/ref. 5.9 Mo Preparation work/ paper work See also checklist at 6.9 Tue 1 color exp, 2hv = (Ry) MOBO 7.9 We 1 color exp, 2hv = (Ry) MOBO; power supply broke down 8.9 Thu 1 color exp, 2hv = (Ry) (Use exc. + dye laser); Used MOBO, weak signal; nevertheless a good CH3 image and KER spectrum 9.9 Fri Leak Plan to do the Ry(68684 )peak; not success. 10.9 Sa - 11.9 Su 12.9 1 color exp. 2hv=78370(Ry) Measured CH3+,CH2+,CH+, 79Br+, C79Br+ (NB: center = 685,535) 13.9 1 color exp. 2hv = 67275(Ry) CH3+(shows rings), CH2+ (shoulders and A peak), CH+ 79Br+, C79Br+, C81Br+ (CH279Br+) 14.9 2hv = 68684(Ry) & 2hv = 75905(Ry) CH3+,CH2+, CH+, 79Br+, C79Br CH3+,CH2+, CH+, 79Br+ 15.9 1 color exp. 2hv=74249, 2hv=77165 Try some broad peaks CH3+,CH2+ CH3+,CH2+,79Br+ 16.9 1 color exp. 2hv=79610 2hv=78339 2hv=78431 CH3+,CH2+,79Br+ CH3+ CH3+

To top date Exp. work Center used Comments/ref: 19.9 Mo 2 color exp. probing Br Ry(66019), 533,357 nm (laser scale) Br resonance Alignment work; no reliable results 20.9 Tue MOBO being fixed; Nozzle being fixed 21.9 We 2 color exp. for Br probing Ry(66019; ) Ry(67275; ) Ry(72977; ) 22.9 Thu 2 color exp. for Br probing Ry(68684; ) Ry(75905; ) 23.9 Fri MOPO not working Problems with laser 24.9/25.9 Sa/ Su AK: Three mountains; AH: Heraklion 26.9 2 color exp. Br probing; plan: Ry(79610: ) Ry(77165; ) Did not work 27.9 2 color exp. Br probing; plan : Ry(79610: ) Ry(77165; ) 2 color exp. Br* probing; plan : Ry(72977; ) Did notwork, Mopo too weak power : NO OK, worked 28.9 2 color exp. Br* probing; plan : Ry(68684; ) 29.9 2 color exp. Br* probing; plan : Ry(75905; ) Ry(66019; ) OK OK; AH & AK left for Iceland 30.9 2 color exp. Br* probing: Ry(67275; ) OK 1.10 Sa 2.10 Su

To top date Exp. work Center used Comments/Refs: 7.10 Fri 1 color exp. (dye laser) 2hv = (Ry) / problem with MOPO 13.10 Thu PES spectra 14.10 / problem with MOPO and Dye laser 8.11 Tue 2 color exp. for CH3 (000)probing Ry(72977; ) Noisy spectrum 10.11 2 color exp. for CH3 (211)probing Ry(72977; )

Check-list for experimental progress and processing work:
To top See: Appearance, :

Two-color experiments, Br and Br* detections:
Br: Dye laser = nm => nm (SHG) => 2hv = cm-1 Br*: Dye laser = nm => nm (SHG) => 2hv = cm-1 To top Exp. Difference= 12.5 cm-1 Difference= 12.6 cm-1 sheet = „various things“

Dye lasers / probe transitions
To top Dye lasers / probe transitions [3/2]np;w [1/2]np;w [3/2]nd;w n3 n2 [1/2]nd;w Br* Br**(2D3/2) Br Br**(4P3/2) sheet = „various things“ REMPI spectra pxp; Gr:0; Lay:0

KERtotal = KERBr + KERCH3 KERBr= mCH3/mCH3 Br* KERtotal
To top KERtotal = KERBr + KERCH3 KERBr= mCH3/mCH3 Br* KERtotal KERCH3= mBr/mCH3 Br* KERtotal hv Eint(CH3) = internal energy of CH3 CH3 + Br D0 CH3Br KERtotal = hv – D0 - Eint(CH3) KERBr = mCH3/mCH3 Br (hv – D0 - Eint(CH3)) KERCH3= mBr/mCH3 Br(hv – D0 - Eint(CH3))

KERt = 0 KERtotal = KERBr + KERCH3 = 0
KERBr= mCH3/mCH3 Br* KERtotal= 0 KERCH3= mBr/mCH3 Br* KERtotal = 0 Eint(CH3) = internal energy of CH3 = hv – D0 hv CH3 + Br D0 CH3Br

KERt = hv – D0 „the CH3 + Br threshold“ for the „Br+ KER“
KERtotal = hv – D0 KERBr= mCH3/mCH3 Br (hv – D0) KERCH3= mBr/mCH3 Br (hv – D0) hv Eint(CH3) = internal energy of CH3= 0 CH3 + Br D0 CH3Br

Various processing procedures (examples):
90

Various processing procedures (examples):
See also: Slides 3-4

CH3 detection: 1) 2) Notes from ;1 (in Crete): use 211, 222, 233. ; see definition:

Lowest energy formation threshold: Second lowest Formation threshold:
Third lowest formation threshold fourth lowest formation threshold fifth lowest formation threshold sixth lowest formation threshold C+ (C++HBr+H2+e-) (C++H+H2+Br-) (C++H+H2+Br+e-) (C++2H+HBr+e-) (C++3H+Br-) (C++3H+Br+e-) CH+ (CH++H2+Br-) (CH++H2+Br) (CH++H+HBr+e-) (CH++2H+Br-) (CH++2H+Br+ +e-) CH2+ (CH2+ + HBr) (CH2+ + H + Br-) (CH2++H+Br) CH3+ (CH3++Br-) (CH3++Br+e-) CBr+ (CBr++H2+H+e-) (CBr++3H+e-) CHBr+ (CHBr++H2+e-) (CHBr++2H+e-) CH2Br+ (CH2Br+ + H + e-) CH3Br+ (CH3Br+(3/2)+e-) (CH3Br+(1/2)+e-) Br+ (CH3 + Br++e-) - H+ ath slide 2

Number of photons needed to reach thresholds for resonance excitation to cm-1 Rydberg / (3/2)5p;0 system: ion Lowest energy formation threshold: Second lowest Formation threshold: Third lowest formation threshold fourth lowest formation threshold fifth lowest formation threshold sixth lowest formation threshold C+ 5 (C++HBr+H2+e-) 5 (C++H+H2+Br-) 6 (C++H+H2+Br+e-) 6 (C++2H+HBr+e-) 6 (C++3H+Br-) 7 (C++3H+Br+e-) CH+ 4 (CH++H2+Br-) 5 (CH++H2+Br) 5 (CH++H+HBr+e-) 5 (CH++2H+Br-) 6 (CH++2H+Br+ +e-) CH2+ 4 (CH2+ + HBr) 4 (CH2+ + H + Br-) 5 (CH2++H+Br) CH3+ 3 (CH3++Br-) 4 (CH3++Br+e-) CBr+ 5 (CBr++H2+H+e-) 6 (CBr++3H+e-) CHBr+ 5 (CHBr++H2+e-) 6 (CHBr++2H+e-) CH2Br+ 4 (CH2Br+ + H + e-) CH3Br+ 3 (CH3Br+(3/2)+e-) 3 (CH3Br+(1/2)+e-) Br+ 4 (CH3 + Br++e-) - H+ ath slide 11

resonance non-resonance [3/2]np;w [1/2]np;w [3/2]nd;w [1/2]nd;w 5 6 7
2 n = w = 4 n3 n2 n1 resonance non-resonance …………………………. ………….…………………………………………………… (1) (2) (3) (4) (5) (6) (7) (8) (9) (10)

I(M+)/I(CH3+) (M = Br, CBr) vs CH3+ REMPI spectrum
I(79Br+)/I(CH3+) I(CH+)/I(CH3+) I(M+)/I(CH3+) (M = Br, CBr) vs CH3+ REMPI spectrum 2hn / cm-1 ; Lay4, Gr11

CH3 Br* KERCH3 / eV KERBr / eV Range of detection on eV scale: Far out
2hv with CH3(X)+Br/Br* 3hv with CH3(X)+Br/Br* 1hv with CH3(X)+Br/Br* 3hv with CH3**+Br/Br* CH3 Far out 1.5 2.9 4.0 KERCH3 / eV 3hv** 1hv(x) 2hv(x) 3hv(x) Br* KERBr / eV 1.0 2.0 2.6 Dropbox….REMPI/From Arnar/CH3Br/Article_two_color/Petros_questions.pptx

Updated (p:15-16, refs. & p:50-51)

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Updated (p:15-16, refs. & p:50-51)

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