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Endoergic ion-molecule-collision processes of negative ions in collisions of I- on CO
Volume 60A, number 1
PHYSICS LETFERS
24 January 1977
ENDOERGIC ION-MOLECULE-COLLISION PROCESSES OF NEGATWE IONS IN COLLISIONS OF 1 ON CO D. VOGT and J. MISCHKE I. Institut für Experimentalphysik, Universitàt Hamburg, Germany Received 28
October 1976
The energy dependence of the cross sections for different ion-molecule-reactions by collisions of 1 on CO has been
measured in the energy range from 0 to 100 eV (lab.). The existence of JC could be established.
Two body reactions of I with CO and the existence of JC have not previously been reported. For the three differeht endoergic reaction channels J
+CO~JO +C
(1)
J
+CO-~O +(J+C)
(2)
j
(3) the energy depefidence of the cross sections has been measured. From the thresholds a lower limit of the electron affinities for CJ and JO and for the dissociation energy of Ci has been evaluated. The experiments reported here were carried out using an apparatus, described in detail elsewhere [1]. This apparatus permitted us to measure the cross section of single collisions in the gas phase by the crossedbeam-method. All reported measurements were carried out in forward direction (0 = 0°).The primary F ions were produced in an electron impact source from CH3J. After mass and energy analysis (fwhm 0.2 eV) the primary J beam is accelerated by a lens system onto the CO target gas beam. The produced secondary ions were analysed by a quadrupole mass spectrometer. In the primary energy range from 0 to 100 eV (lab.) the production of iC, i0 and O has been observed. The energy dependence of the cross sections for the different ion-molecule-reactions is shown in figs. 1,2, and 3. From the threshold of reaction (1) in fig. 1, a lower limit of the electron affinity of JO can be deduced, if all reactants and products are in ground states. With the known electron affinity of J (EA(J) = 3.06 eV [2]) and dissociation energies for CO (D(DO) = 11.09 eV [3]) and JO (D(JO) 2.0 eV [3]) the lower limit of the electron affinity for JO results in EA(i0) ~ 2.5 eV
-.‘ -,
as
s~
‘
9B~ 9
~
25
~
E~tCMeV)
I
Fig. 1. Cross section ofthe reaction J
+
CO —~ JO
+
C.
at a threshold of E~= 9.5 eV. This is in agreement with earlier measurements [4] of the reaction J + 02 -÷J0 + 0 in which a value of EA(JO)~2.1 eV has been calculated. The cross section for the ion-molecule-reaction J + CO -~ O + is shown in fig. 2. For this reaction there are two possible exit channels: —~ 0 + JC, and ...
,.-
‘-~
-‘
:-‘
~~‘i ,-8.0 .
89
—
I
198
07
flS
12.S
13.4
~
~ EpCCM,eVl
+
CO —~ O~+....
Et
Fig. 2. Cross section of the reaction J
19
Volume 60A, number 1
PHYSICS LETIERS
Fig. 3 shows the cross section for the production a molecular negative ion the existence of which has not previously been reported. With the dissociation energy of JC, estimated above, and the electron affinity of J, the dissociation energies of CO and the threshold at = 9.5 eV a lower limit of EA(JC) ~ 1.96 eV could be estimated.
O3~
of JC,
co —_ic.o
T
89
1
I
89
~
I
I
~8
10,7
11,6
24 January 1977
I
12~
I
I
l~4
l~,3
16,1
I
ViO
E~[CMeV]
1
Fig. 3. Cross section of the reaction F
I
I
l~2
E
We gratefully acknowledge financial support by the Deutsche Forschungsgemeinschaft.
+
CO —~JC
+
0.
References
—~O + J + C, respectively. From the threshold at Et = 10.0 eV, the electron affinities of J~(s.a.) and 0 (EA(O) = 1.46 eV [2]) and the disssociation energy of
[I] D. Vogt, J. Mischke and W. Dreves, J. Phys. E8 (1976).
CO (s.a.) a lower limit of the binding energy of JC can be evaluated to D(JC) ~i’ 2.69 eV. This is in agreement with a rough estimation by flame reactions of the type
London, 1968). [4] D. Vogt, W. Dreves and J. Mischke, Intern. J. Mass Spec, trom. Ion Phys., to be published.
C + JC = C2 + J, which suggest a value of about D(JC) = 2.2 eV [5].
20
[21 McDaniel and McDowell, Case studies in atomic collision physics (North-Holland, Amsterdam, 1972) p. 530. [31 A.G. Gaydon, Dissociation energies (Chapman and Hall,
[51 W.J. Miller 3701.
and H.B. Palmer, J. Chem.
Phys. 40
(1964)
PHYSICS LETFERS
24 January 1977
ENDOERGIC ION-MOLECULE-COLLISION PROCESSES OF NEGATWE IONS IN COLLISIONS OF 1 ON CO D. VOGT and J. MISCHKE I. Institut für Experimentalphysik, Universitàt Hamburg, Germany Received 28
October 1976
The energy dependence of the cross sections for different ion-molecule-reactions by collisions of 1 on CO has been
measured in the energy range from 0 to 100 eV (lab.). The existence of JC could be established.
Two body reactions of I with CO and the existence of JC have not previously been reported. For the three differeht endoergic reaction channels J
+CO~JO +C
(1)
J
+CO-~O +(J+C)
(2)
j
(3) the energy depefidence of the cross sections has been measured. From the thresholds a lower limit of the electron affinities for CJ and JO and for the dissociation energy of Ci has been evaluated. The experiments reported here were carried out using an apparatus, described in detail elsewhere [1]. This apparatus permitted us to measure the cross section of single collisions in the gas phase by the crossedbeam-method. All reported measurements were carried out in forward direction (0 = 0°).The primary F ions were produced in an electron impact source from CH3J. After mass and energy analysis (fwhm 0.2 eV) the primary J beam is accelerated by a lens system onto the CO target gas beam. The produced secondary ions were analysed by a quadrupole mass spectrometer. In the primary energy range from 0 to 100 eV (lab.) the production of iC, i0 and O has been observed. The energy dependence of the cross sections for the different ion-molecule-reactions is shown in figs. 1,2, and 3. From the threshold of reaction (1) in fig. 1, a lower limit of the electron affinity of JO can be deduced, if all reactants and products are in ground states. With the known electron affinity of J (EA(J) = 3.06 eV [2]) and dissociation energies for CO (D(DO) = 11.09 eV [3]) and JO (D(JO) 2.0 eV [3]) the lower limit of the electron affinity for JO results in EA(i0) ~ 2.5 eV
-.‘ -,
as
s~
‘
9B~ 9
~
25
~
E~tCMeV)
I
Fig. 1. Cross section ofthe reaction J
+
CO —~ JO
+
C.
at a threshold of E~= 9.5 eV. This is in agreement with earlier measurements [4] of the reaction J + 02 -÷J0 + 0 in which a value of EA(JO)~2.1 eV has been calculated. The cross section for the ion-molecule-reaction J + CO -~ O + is shown in fig. 2. For this reaction there are two possible exit channels: —~ 0 + JC, and ...
,.-
‘-~
-‘
:-‘
~~‘i ,-8.0 .
89
—
I
198
07
flS
12.S
13.4
~
~ EpCCM,eVl
+
CO —~ O~+....
Et
Fig. 2. Cross section of the reaction J
19
Volume 60A, number 1
PHYSICS LETIERS
Fig. 3 shows the cross section for the production a molecular negative ion the existence of which has not previously been reported. With the dissociation energy of JC, estimated above, and the electron affinity of J, the dissociation energies of CO and the threshold at = 9.5 eV a lower limit of EA(JC) ~ 1.96 eV could be estimated.
O3~
of JC,
co —_ic.o
T
89
1
I
89
~
I
I
~8
10,7
11,6
24 January 1977
I
12~
I
I
l~4
l~,3
16,1
I
ViO
E~[CMeV]
1
Fig. 3. Cross section of the reaction F
I
I
l~2
E
We gratefully acknowledge financial support by the Deutsche Forschungsgemeinschaft.
+
CO —~JC
+
0.
References
—~O + J + C, respectively. From the threshold at Et = 10.0 eV, the electron affinities of J~(s.a.) and 0 (EA(O) = 1.46 eV [2]) and the disssociation energy of
[I] D. Vogt, J. Mischke and W. Dreves, J. Phys. E8 (1976).
CO (s.a.) a lower limit of the binding energy of JC can be evaluated to D(JC) ~i’ 2.69 eV. This is in agreement with a rough estimation by flame reactions of the type
London, 1968). [4] D. Vogt, W. Dreves and J. Mischke, Intern. J. Mass Spec, trom. Ion Phys., to be published.
C + JC = C2 + J, which suggest a value of about D(JC) = 2.2 eV [5].
20
[21 McDaniel and McDowell, Case studies in atomic collision physics (North-Holland, Amsterdam, 1972) p. 530. [31 A.G. Gaydon, Dissociation energies (Chapman and Hall,
[51 W.J. Miller 3701.
and H.B. Palmer, J. Chem.
Phys. 40
(1964)