Gaseous Ions and Chemical Mass Spectrometry Diethard K. Böhme Ion Chemistry Laboratory Department...
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Gaseous Ions and Chemical Mass Spectrometry Diethard K. Böhme Ion Chemistry Laboratory Department of Chemistry Centre for Research in Mass Spectrometry Centre for Research in Earth & Space Science York University, Toronto, Canada CIC Medal Lecture Winnipeg, 2007
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Transcript of Gaseous Ions and Chemical Mass Spectrometry Diethard K. Böhme Ion Chemistry Laboratory Department...
Gaseous Ions and Chemical Mass Spectrometry
Diethard K. Böhme
Ion Chemistry Laboratory
Department of Chemistry Centre for Research in Mass Spectrometry
Centre for Research in Earth & Space ScienceYork University, Toronto, Canada
CIC Medal LectureWinnipeg, 2007
Gaseous Ions_____________________________________________________
C+, Fe+, Si+, Mg+
H3+
CH5+
N2H+
O2+, N2
+
HCO+
H3O+, HCNH+
HC3NH+
NH2OH+
+H3NCH2CH2COOH
O2-
OH-, CH3O-
H3O+
OH- (H2O)n
CH3O- (CH3OH)n
H3O+ (H2O)n
C2+, C3
+, CN+
C3H3+, SiC10H8
+
FeC6H6+
HO
N
NN
N
NH2
O
HO
HH
H
CH2
H
PO
-O
OCH2
O
H
HH
HH
O
H
HH
HH
HN
N
O
O
CH3
O
H
HH
HH
N
N
NH2
O
NH
N
N
O
NH2N
O
H
HH
HHOH
NH
N
N
O
NH2N
O
H
HH
HH
HN
N
O
O
CH3
O
PO
-O
OCH2
O
PO
-O
OCH2
O
PO
-O
OCH2
O
PO
-O
OCH2
NH
ON
S
O
O
OH
O
Zn2+
N
S
SN
O
NH
S+CH3
H3C
NH
OH
HO CH3H
HN
O
H CH3HO
H
CH3H
NH
OHHN
OOH
O
O
NH2O
OH
HO
O
HO
HO OHO
H
N
NH
ON N
CH3
H2N
H
NHH NH2
O
NH2
O NH2
_________________________________________________________________
“Ions are jolly little buggars, you can almost see them“ Ernest Rutherford
Sr(C60)4+
Cu
N
N
N
N
N
NN
N
SO-
OO
SONa
OO
SO- O
O
S
O-
OO
C+, Fe+, Si+, Mg+
H3+, CH5
+, N2H+, HCO+
HCNH+, HC3NH+, SiC4H+, SiC10H8+
CH3+, C2H2
+, C2H3+, C3H
+, C3H3+, C4H3
+
C3N+, HCN+, HC3N
+, C60+, C60
++, C60X+
NH2OH+, +H3NCH2CH2COOH
O-, O2-, OH-, OH- (H2O)n
H3O+, H3O
+ (H2O)n
CH3CNH+
Ionospheric,Cometary and
Interstellar Ions
Ions Found inSolution
2+ Cu
N
N
N
N
N
NN
N
SO-
OO
SONa
OO
SO- O
O
S
O-
OO
OH-, CH3O-, C2H5O-, (CH3)3CO-
C6H5-, C6H5CH2
-, C6H5C(CH3)2-, t-BuC6H5
-,
H3O+ (H2O)n, OH- (H2O)n, CH3O- (CH3OH)n,
C2H5O-(C2H5OH)n, Ca2+, Sr2+, Ba2+, H3O+
C+, C2+, C3
+, C6H6+, C60
n+, C70n+
Fe+benzene, Fe+coronene
Si+benzene, Si+naphthalene
Carbonaceous IonsAtomic Cations
Fe+ Mg+
Pt+
La+Si+
K+
Ca+
Sc+
Ti+
Ar+
V+
Cr+
Mn+
Co+
Ni+
Cu+
Zn+
Ga+
Ge+
As+
Se+
Rb+
Sr+
Y+
Zr+
Nb+
Mo+
Ru+
Rh+
Pd+
Ag+
Cd+
In+Sn+
Sb+
Te+
Cs+
Ba+
Hf+
Ta+
W+
Re+
Os+
Ir+
Au+
Hg+
Tl+
Pb+
Bi+
Ce+
Pr+
Nd+Sm+
Eu+
Gd+
Tb+
Dy+
Ho+
Er+
Tm+
Yb+
Lu+
HO
N
NN
N
NH2
O
HO
HH
H
CH2
H
PO
-O
OCH2
O
H
HH
HH
O
H
HH
HH
HN
N
O
O
CH3
O
H
HH
HH
N
N
NH2
O
NH
N
N
O
NH2N
O
H
HH
HHOH
NH
N
N
O
NH2N
O
H
HH
HH
HN
N
O
O
CH3
O
PO
-O
OCH2
O
PO
-O
OCH2
O
PO
-O
OCH2
O
PO
-O
OCH2
HO
N
NN
N
NH2
O
HO
HH
H
CH2
H
PO
-O
OCH2
O
H
HH
HH
O
H
HH
HH
HN
N
O
O
CH3
O
H
HH
HH
N
N
NH2
O
NH
N
N
O
NH2N
O
H
HH
HHOH
NH
N
N
O
NH2N
O
H
HH
HH
HN
N
O
O
CH3
O
PO
-O
OCH2
O
PO
-O
OCH2
O
PO
-O
OCH2
O
PO
-O
OCH2
Biological Ions
N
S
SN
O
NH
S+CH3
H3C
NH
OH
HO CH3H
HN
O
H CH3HO
H
CH3H
NH
OHHN
OOH
O
O
NH2O
OH
HO
O
HO
HO OHO
H
N
NH
ON N
CH3
H2N
H
NHH NH2
O
NH2
O NH2
(AGTCTG-5H+)5-
NH
ON
S
O
O
OH
O
Zn2+
Fe3+siderophore
bleomycin+
Zn2+penicillin
Looking for Ions in a Flowing Nitrogen Discharge Plasma ______________________________________________________
First quadrupole mass spectra (in Canada)
_____________________________________________________Mass Spectrometric Sampling Probe for Discharge PlasmasD.K. Böhme, J.M. Goodings. Rev. Sci. Instr. 37 (1966) 362.Ion Sampling Considerations for a Discharge Plasma of NitrogenD.K. Böhme, J.M. Goodings. J. Appl. Phys. 37 (1966) 4261.
Ion Chemistry in a Flowing Helium Plasma ______________________________________________________
kA+ + B products
- d[A+]/dt = k [A+][B]
-v d[A+]/dz = k [A+][B]
[A+]z = [A+]z=0 exp(-k[B]z/v)
t = z/v
[B] >> [A+]
In He at 0.35 Torr, 296 K(O2 + e O+, O2
+ + 2e)
O+ + H2 OH+ + HOH+ + H2 H2O+ + HH2O+ + H2 H3O+ + H_______________________________________________________________________________________________________________________________________________
Fehsenfeld, F. C.; Schmeltekopf, A. L.; Ferguson, E. E. “Thermal-energy ion-neutral reaction rates. VII. Some hydrogen-atom abstraction reactions.” J. Chem. Phys. 46 (1967) 2802-8.
O+
O2+
pseudo1st orderkinetics
Slope = - k z/v
Plasma Ions Upstream:
e + H2O OH- + H OH-(H2O)n + H2O + He OH-(H2O)n+1- + He
e + H2O H2O+ + 2e H2O+ + H2O H3O+ + OH H3O+ (H2O)n + H2O + He H3O+ (H2O)n + He
In the complete absence of bulk solvent !
SN2 : OH- + CH3Cl Cl- + CH3OHAcid-Base : OH- + CH3OH CH3O- + H2O
H3O+ + CH3OH CH3OH2+ + H2O
As a function of step-wise molecular solvation !
OH- (H2O)n + CH3Cl Cl- (H2O)n + CH3OH OH- (H2O)n + CH3OH CH3O- (H2O)n + H2O
H3O+ (H2O)n + CH3OH CH3OH2+(H2O)n + H2O
Getting at the Heart of Chemistry_____________________________________________________
Plasma Ions Upstream:
e + H2O OH- + H OH-(H2O)n + H2O + He OH-(H2O)n+1- + He
e + H2O H2O+ + 2e H2O+ + H2O H3O+ + OH H3O+ (H2O)n + H2O + He H3O+ (H2O)n + He
In the complete absence of bulk solvent !
SN2 : OH- + CH3Cl Cl- + CH3OHAcid-Base : OH- + CH3OH CH3O- + H2O
H3O+ + CH3OH CH3OH2+ + H2O
As a function of step-wise molecular solvation !
OH- (H2O)n + CH3Cl Cl- (H2O)n + CH3OH OH- (H2O)n + CH3OH CH3O- (H2O)n + H2O
H3O+ (H2O)n + CH3OH CH3OH2+(H2O)n + H2O
Getting at the Heart of Chemistry_____________________________________________________
OH- + CH3Cl Cl- + CH3OHk = 1.5 x 10-9 cm3 molecule-1 s-1!! [cf: 10-26 in H2O]
__________________________________________________________________________________________Gas-phase reactions of anions with halogenated methanes at 297 ± 2K.K. Tanaka, G.I. Mackay, J.D. Payzant, D.K. Bohme. Can. J. Chem. 54, 1643-59 (1976). Bridging the gap between the gas phase and solution: transition in the kinetics of nucleophilic displacement reactions.D.K. Bohme, G.I. Mackay. J. Am. Chem. Soc. 103, 978-9 (1981).
Transition from the Gas Phase to Solution_____________________________________________________________
T = 298 K
Transition from the Gas Phase to Solution (cont’d)_____________________________________________________
_______________________________________________________________Standard acidity scale. The pKa of alcohols in the gas phase.D.K. Bohme, E. Lee-Ruff, L.B. Young. J. Am. Chem. Soc. 93, 4608-9 (1971). Acidity order of selected Broensted acids in the gas phase of 300K.D.K. Bohme, E. Lee-Ruff, L.B. Young. J. Am. Chem. Soc. 94, 5153-9 (1972). Bridging the gap between the gas phase and solution: transition in the relative acidity of water and methanol at 296 ± 2 K. G.I. Mackay, D.K. Bohme. J. Am. Chem. Soc. 100, 327 (1978).
OH- + CH3OH CH3O- + H2O, k = 1.5 x 10-9 cm3 molecule-1 s-1
2962 K K = 2.2 x 107, Go = - 9.9 kcal mol-1
X- + YH Y- + XHXH+ + Y YH+ + X
________________________________________________________________________________________Determination of proton affinities from the kinetics of proton transfer reactions. VII. The proton affinities of O2, H2, Kr, O, N2, Xe, CO2, CH4, N2O, and CO. D.K. Bohme, G.I. Mackay, H.I.
Schiff. J. Chem. Phys. 73, 4976-86 (1980).
XH+ + Y YH+ + X
Proton-Transfer and Proton Affinities__________________________________________________________
Selected-Ion Flow Tube (SIFT) Tandem Mass Spectrometry______________________________________________________
____________________________________________________________________________________________Studies of reactions involving C2Hx
+ ions with hydrogen cyanide using a modified selected ion flow tube.
G.I. Mackay, G.D. Vlachos, D.K. Bohme, H.I. Schiff. Int. J. Mass Spectrom. & Ion Physics, 36, 259 (1980). Ion-molecule reactions with carbon chain molecules: reactions with diacetylene and the diacetylene cation. S. Dheandhanoo, L. Forte, A. Fox, D.K. Bohme. Can. J. Chem. 64, 641-8 (1986)
ElectronImpactM
Sifting Ions: One Major Reactant Ion
(no Electrons)
C4H2+ + C4H2 C8H4
+
C6H2+ + C2H2
C6H2+ + C4H2 C10H4
+
________________________________________________________________
Ionic Origins of Carbenes in Space. D.K. Bohme. Nature 319, 473-4 (1986)
Ionic Origins of Carbenes in Space______________________________________________________
Carbenes occur widely in the Universe
:CH2, :C=C:, :C=S, :C=O, :C =NH, :C=C=C:, l,c-:C3H2, :C3OTheir origin may involve ionizing radiation.
Only H2C4: has not yet been observed in space.
e + propylene C3H+
Mg(HC3N)n-1+ + HC3N Mg(HC3N)n
+ + h, n 0
Mg(HC3N)n+ + e (HC3N)n + Mg
N N
NC
C
CC
N + Mg+ eCN
CN
CC
N
N
Mg+
_______________________________________________________________Extraordinary Cluster Formation and Intramolecular Ligand-Ligand Interactions in Cyanoactylene Mediated by Mg +·: Implications for the Atmospheric Chemistry of Titan and for Circumstellar Chemistry. Rebecca Milburn, Alan C. Hopkinson, Diethard K. Bohme, J. Am. Chem. Soc. 127 (2005)13070-78.
Tetracyanocyclooctatetraene (Tetracyanosemibullvalene)
Circumstellar Envelopes
Titan’s Atmosphere
mCID
Synthesis of Exotic Carbon Rings______________________________________________________
NH3(s) + H2O(s) NH2OHh h NO + 3H
h, heat
NH2OH
Interstellar ice
Interstellar gas
h/A+ RH+
NH2OH2+NH2OH+
CH3COOHCH3CH2COOH
CH3COOHCH3CH2COOH
NH2CH2COOH+
NH2CH2CH2COOH+
NH3CH2COOH+
NH3CH2CH2COOH+
-H2O-H2O
MM+
NH2CH2COOHNH2CH2CH2COOH
e-
H
_______________________________________________________________________________
Gas-phase syntheses for interstellar carboxylic and amino acids.Blagojevic et al., Mon. Not. R. Astron. Soc. 339 (2003) L7-L11.
Ions and Life_______________________________________________________
_______________________________________________________________________________Fullerene Cation and Dication Production by Novel Thermal-Energy Reactions of He+, Ne+, and Ar+ with C60. G. Javahery, S. Petrie, J. Wang and D.K. Bohme. Chem.
Phys. Lett., 195, 7-10 (1992).Electron-Transfer Reactions with Buckminsterfullerene, C60, in the Gas Phase.
D.K. Bohme, Int. Reviews in Physical Chemistry, 13, 163-185 (1994).
Penning Ionization
He (3S1, 1S1) + C60 He(1S0) + C60+• + e
“Electron Transfer/ Electron Detachment”
He+ + C60 C602+ + He + e
“Double-Electron Transfer/ Electron Detachment”
Ar2+ + C60 C60•3+ + Ar + e
Chemical Ionization of Fullerenes_____________________________________________
Playing Chemistry with Buckyballs____________________________________________________
C60+• C60
2+
_____________________________________________________________________________________________________Derivatization of the Fullerene Dications C60
2+ and C702+ by Ion-Molecule Reactions in the Gas Phase.
S. Petrie, G. Javahery, J. Wang and D.K. Bohme. J. Am. Chem. Soc., 114, 9177-9181 (1992). Gas-Phase Reactions of the Buckminsterfullerene Cations C60
.+, C602+ and C60
.3+ with Water, Alcohols and
Ethers. R. Javahery, S. Petrie, H. Wincel, J. Wang and D.K. Bohme. J. Am. Chem. Soc., 115, 6295-6301 (1993).
______________________________________________________________________C60
3+•
Charge ………!___________________________________________________________
Gas-Phase Reactions of Fullerene Monocations, Dications and Trications with Nitriles.G. Javahery, S. Petrie, J. Wang, H. Wincel and D.K. Bohme. J. Am. Chem. Soc., 115, 9701-9707 (1993).
_______________________________________________________________________Fullerene Ions in the Gas Phase: Chemistry as a Function of Charge State.D.K. Bohme, Can. J. Chem. 77, 1453-1464 (1999).
Chemistry is increasingly pre-empted by physics (e transfer) with increasing charge state.
Chemistry as a Function of Charge State_________________________________________________________________
N C C CH+ +
+ N C C CH+ N C C CH+
N C C CH
+
++
N C C CHNCCHC
+ +·
NC
NC
C
C C
C
H
H
+•
Chemistry and Physics in Concert_______________________________________________________________
C60 provides charged C site for covalent bonding.
• Polar molecule is attracted to the charge.
Electrostatic attraction is sufficient to overcome rehybridization energy required for bonding.
Intramolecular Coulomb repulsion propagates charge to the terminus of thesubstituent and so provides a new atomic site for further reaction.
• Ultimate charge separation.
C602+ + 2 HC3N C60
+• + c-(HC3N)2+•
_________________________________________________________________Milburn et al, J. Phys. Chem. A 103 (1999) 7528.
+ N C C CH+
HC C C N
+
Gas-Phase Surface Chemistry____________________________________________________
_____________________________________________________________________________________________________________________The Influence of Surface Strain on the Chemical Reactivity of Fullerene Ions: Addition Reactions with Cyclopentadiene and 1,3-Hexadiene.. Becker, L.T. Scott and D.K. Bohme, Int. J. Mass Spectrom. Ion Processes 167/168, 519 (1997). Enhanced Reactivity of Fullerene Cations Possessing Adjacent Pentagons. S. Petrie and D.K. Bohme. Nature, 365, 426. (1993).
(C surface)+ + c-C5H6 addition
The Influence of Curvature (Strain)
H HH
H
HH
HH
H
H
Fe
Fe
H HH
H
H
HHH
H
H
H
H
H
H
HHHH
H
H
Fe
FeFe
HH
++
+
+
+
Metal-Cation Ligation
on Curved Carbonaceous Surfaces
The ICP/SIFT/QqQ instrument _____________________________________________________
B low erTrip le Q uadrupole
R eagen tIn le t
H e liumIn le tP lasm a
S ource
D iffus ionP um p
TurboP um p
TurboP um p
TurboP um p
__________________________________________________________________________________________________________An Inductively-Coupled Plasma / Selected-Ion Flow Tube Mass Spectrometer Study of the Chemical Resolution of Isobaric Interferences. G.K. Koyanagi, V.I. Baranov, S. Tanner and D.K. Bohme, J. Anal. At. Spectr. 15, 1207-1210 (2000).
Argon Plasma
5500 K
P = 1 atm
Aqueous solutionof the atomic salt is injected via a nebulizer intothe Ar plasma
Periodic Table of Atomic Salt Solutions
N2O flow/(1017 molecules s-1)0.0 1.0 2.0 3.0 4.0
Ion
Sign
al
100
101
102
103
Nb+
NbN+
NbO2+
NbO2+·N2O
NbO+
NbNO+
NbNO+·N2O
NbNO+·(N2O)2
NbNO+·(N2O)3
NbO2+·(N2O)2
NbO2+·(N2O)3
Primary Oxidation and Nitration
Nb+ + N2O NbO+ + N2
NbN+ + NO
Further Oxidation
NbO+ + N2O NbO2+ + N2
NbN+ + N2O NbNO+ + N2
Clustering with N2O
NbO2+ + N2O NbO2(N2O)+
NbO2(N2O)+ +N2O NbO2(N2O)2+
NbO2(N2O)2+ +N2O NbO2(N2O)3
+
NbNO+ + N2O NbNO(N2O)+
NbNO(N2O)+ +N2ONbNO(N2O)2+
NbNO(N2O)2+ +N2ONbNO(N2O)3
+
Reactions of atomic cations: Nb+ with N2O ______________________________________________________
________________________________________________________________V.V. Lavrov et al., J. Phys. Chem. A 106 (2002) 4581.
Surfing the Periodic Table with N2O______________________________________________________
________________________________________________________________V.V. Lavrov et al., J. Phys. Chem. A 106 (2002) 4581.
M+ + N2O
MO+ + N2
MN+ + NO
M+(N2O)
La Ce Pr Nd Pm Sm Eu Gd Tb Dy Ho Er Tm Yb Lu
k/(c
m3 m
olec
ules
-1 s
-1)
10-12
10-11
10-10
10-9
Pro
mot
ion
Ene
rgy/
(kca
l mol
-1)
0
20
40
60
80
100
4f n5d
0 6s1
4f n
-15d
1 6s1
_____________________________________________________G.K. Koyanagi, D.K. Bohme. J. Phys. Chem. A 105, 8964 (2001).
Ln+ + N2O LnO+ + N2
Barriers to Electron Promotion____________________________________________________
Arrhenius would be interested!____________________________________________________
kexp= kc e-PE/RT
61 atomic cations x 15 molecules = 915 reactions !!
http://www.chem.yorku.ca/profs/bohme/research/research.html
Web data base
The 87Rb+ (s0) / 87Sr+ (s1) Isobaric Interference
Rb+ (s0) + SF6 NR k 1x10-13 cm3 s-1
Sr+ (s1) + SF6 SrF+ + SF5 97% k = 5.7x10-10 cm3 s-1 SrSF5
+ + F 3%
Chemical Resolution in Elemental Analysis____________________________________________________
____________________________________________________C. Ping and D.K. Bohme, J. Phys.Chem. A, in preparation.
Discontinuities in Reactivity: Opportunities for Chemical Resolution
____________________________________________________
M+ + SF6
MFn+ + SF6-n
M+(SF6 )
SFn+ + MF6-n
Observed with:
Fe+, Ge+
Sr+ Ba+, Os+, Ir+
Eu+, Yb+
____________________________________________________Blagojevic et al., Angew. Chem. Int. Ed. 2003, 42, 4923-4927
Observed with:
Fe+, Ge+
Sr+
Ba+, Os+, Ir+
Eu+, Yb+
N2O
N2
(2) NO
CO
M+
MO+
M+
MO+
M+
MO+
NO2CO2
CO2
CO2
CO
CO
Catalytic reduction of NxOy by CO
____________________________________________________Blagojevic et al.,Angew. Chem. Int. Ed. 2003, 42, 4923-4927
Atomic Ions: the Ultimate Sites for Catalysis_____________________________________________
Catalytic Reduction of NxOy by CO
(O-atom Transport Mediated by M+)
C O 2
N 26D F e +
T S
T S
T S
14 .9
61 .8
22 .9
0 .9
30 .6
0 .9
47 .8
47 .2
86 .7
64 .1
NOCF e
N 2O + C O N 2 + C O 2
F e + + N 2O F eO + + N 2
F eO + + C O F e + + C O 2
C O
C O
C O
C O N 2
N 2
N 2
C ON 2O6D F e +
H /k ca l m ol -1
__________________________________________________________________ V. Blagojevic, G. Orlova, D. K Bohme, J. Am. Chem. Soc. 127 (2005) 3545.
GAUSSIAN98 B3LYP/sdd/6-311+G*
Potential Energy Landscape for Catalysis______________________________________________________
ICP/SIFT/QqQ mass spectrumProposed tetrahedralstructure for Sr(C60)4
+
0 500 1000 1500 2000 2500 3000100
101
102
103
104
105
106
SrC60
+
Sr(C60
)2
+
Sr(C60
)3
+
Sr+
Inte
nsi
ty
m/z
Sr(C60
)4
+
Packing Atomic Metal Cations with C60
_____________________________________________________
_______________________________________________________________________G.K. Koyanagi, J. Xu and D. K. Bohme, unpublished
The ESI/qQ/SIFT/QqQ instrument_____________________________________________________
A – skimmer, B – q0 reaction cell, C extended stubbies, D – extended q0 rod set
_________________________________________________________________________________________A novel chemical reactor suited for studies of biophysical chemistry: construction and evaluation of a selected ion flow tube utilizing an electrospray ion source and a triple quadrupole detection system. G.K. Koyanagi et al. Int. J. Mass Spectrom. In press, 2007.
Ca++ + O3 CaO+ + O2+
(k = 1.5 × 10-9 cm3 mol-1 s-1) CaO+ + O3 CaO2
+ + O2
(k = 5 × 10-10 cm3 mol-1 s-1)
CaO2+ + O3 CaO3
+ + O2
(k = 6 × 10-10 cm3 mol-1 s-1)
100 M CaAcetate in H2O/CH3OH (1/1)
From Atomic Dications…._____________________________________________________
Oxidation of Ca++ Initiated by Charge Separation.
…..to DNA_______________________________________________________________________________
Protonation and Hydrobrominationof (AGTCTG-5H)5-
50 M in 20/80 CH3OH/H2O
HO
N
NN
N
NH2
O
HO
HH
H
CH2
H
PO
-O
OCH2
O
H
HH
HH
O
H
HH
HH
HN
N
O
O
CH3
O
H
HH
HH
N
N
NH2
O
NH
N
N
O
NH2N
O
H
HH
HHOH
NH
N
N
O
NH2N
O
H
HH
HH
HN
N
O
O
CH3
O
PO
-O
OCH2
O
PO
-O
OCH2
O
PO
-O
OCH2
O
PO
-O
OCH2
+ HBr
kobs kobs/kc
3.2 0.68
2.6 0.78
1.9 0.77
1.3 0.80x10-9 cm3 s-1
80% n = 1-7
27% n = 1-7 5–
4–
3–
2–
73%
16% n = 1-6
84%
20%
100% n = 1-5
HBr
HBr
HBr
[(AGTCTG − 5H)(HBr)n]5−
[(AGTCTG − 4H)(HBr)n]4−
[(AGTCTG − 3H)(HBr)n]3−
[(AGTCTG − 2H)(HBr)n]2−
0.0 0.4 0.8 1.2 1.610
0
101
102
103
104
5
n=1[(AGTCTG-2H)(HBr)
n]2
6
n=1[(AGTCTG-4H)(HBr)
n]4
7
n=1[(AGTCTG-3H)(HBr)
n]3
(AGTCTG-5H)5
(AGTCTG-4H)4
(AGTCTG-3H)3
(AGTCTG-2H)2
Ion
Sig
na
l/(s
1)
HBr flow/(1017
molecules s1
)
7
n=1[(AGTCTG-5H)(HBr)
n]5
Greg Koyanagi Stefan FeilJanna AnichinaVoislav Blagojevic Michael JarvisAndrea DasicTuba Gozet Sara HashemiMike DuhigSvitlana Shcherbyna
Acknowledgments
