Engineering Sciences Reports, Kyushu University
Vol. 45, No. 1, pp. 13-24, SEP, 2023

九州大学大学院総合理工学府報告第 45 巻 1 号 13-24 頁 令和 5 年 9 月

Spin-orbit State Selectivity in the Formation ofRgCl(B,C,D) Excimers from Ion-Ion Recombination
Reactions of Rg+ with C6F5Cl- in the Flowing Afterglow
Masaharu TSUJI,*1,2† Hiroaki ISHIMI,*3 Keiko UTO,*1
Jun-Ichiro HAYASHI*1 and Takeshi TSUJI*4
E-mail of corresponding author: tsuji@cm.kyushu-u.ac.jp†(Received March 27, 2023, accepted April 18, 2023)
RgCl(B,C,D) excimers were produced for Rg = Ar, Kr, and Xe by the positive ion-negative ion
recombination reactions of Rg+(2P1/2,3/2) with C6F5Cl- in the flowing afterglow. Spin-orbit state
selectivity of RgCl(B,C,D) excimers by the Rg+(2P1/2) and Rg+(2P3/2) components was examined by using
appropriate filter gases of one spin-orbit component. The RgCl(B,D) ratio was determined to be
0.35:0.65, 0.05:0.95, and 0.24:0.76 in the Ag+(2P1/2), Kr+(2P1/2), and Xe+(2P1/2) reactions, whereas the
RgCl(B,C) ratio was estimated to be 0.74:0.26, 0.71:0.29, and 0.70:0.30 in the Ag+(2P3/2), Kr+(2P3/2), andXe+(2P3/2) reactions, respectively. The Rg+(2P1/2) reactions had a high propensity to give RgCl(D) plus a
lesser amount of RgCl(B), whereas the Rg+(2P3/2) reactions gave only RgCl(B,C). These results showthat Rg+(2P1/2) + Cl- and Rg+(2P3/2) + Cl- characters are conserved well for the formation of RgCl* in theion-ion recombination reactions between Rg+(2P1/2,3/2) and C6F5Cl-. Higher conservation of Rg+(2P1/2)
character in the Rg+(2P1/2)/C6F5Cl- reactions than that in the Rg(3P0)/halides reactions is discussed byusing correlation diagram between entrance and exit product channels.
Key words: Positive ion-negative ion reaction, Recombination reaction, RgCl* excimer, Ar+, Kr+, Xe+,

C6F5Cl -, Flowing afterglow, Emission spectroscopy, Spin-orbit state selectivity,
Correlation diagram

1.

Introduction

We have successfully applied the flowing
afterglow apparatus to the study on two-bodydissociative ionic-recombination reactions1-4)
Rg+(2P1/2,3/2) + SF6- → RgF(B,C,D) + SF5, (1)where Rg represents Ar, Kr, or Xe atom.
Positive Rg+(2P1/2,3/2) ions were formed by
He(23S)/Rg Penning ionization and negative
SF6- ions were produced by attachment of
Penning electrons to SF6. The spin-orbit state
selectivity in the KrF* and XeF* formation was
examined by selecting one of the spin-orbit
components of Kr+ and Xe+, 2P1/2 or 2P3/2. It was
found that Kr+ and Xe+ ions in the 2P1/2 level*1 Institute for Materials Chemistry and Engineering,and Research and Education Center of GreenTechnology*2 Department of Molecular Science and Technology*3 Department of Molecular Science and Technology,
Graduate Student*4 Department of Materials Science, Shimane
University

preferentially give the D state, while those in
the 2P3/2 level give only the B and C states. The
high spin-orbit state selectivity was explainedby the conservation of Rg+(2P1/2) + F- andRg+(2P3/2) + F- characters.
In this study, ion-ion recombination
reactions of Ar+(2P1/2,3/2), Kr+(2P1/2,3/2), andXe+(2P1/2,3/2) with C6F5Cl- are studied byobserving RgCl* excimer emissions in theflowing afterglow. By using various filter gasesof one spin-orbit component, effects of spinorbit state are examined. Results obtained arecompared with previous data for the formationof RgX* (X = halogen) excimers from the ion-ion
recombination reactions of Rg+(2P1/2,3/2)/SF6- (Rg= Kr, Xe)2) and from energy-transfer reactionsof Ar(3P0,2) with simple halides.5-7)

2.

Experimental

2.1

Chemicals

Rare gases, filter gases used for spin-orbit
state selection, and an electron scavenger
C6F5Cl used in this study were obtained from

Spin-orbit state selectivity for RgCl(B,C,D) excimers produced from recombination reactions of Rg+ with C6F5Cl-

14

Japanese chemical companies: He (purity>99.9999%, Taiyo Sanso), Ar (99.999%, Nippon
Sanso), Kr (99.995%, Nippon Sanso), Xe(99.99%, Nippon Sanso), N2 (99.9999%, Taiyo
Sanso), O2 (99.9%, Nippon Sanso), C2H2 (99%,
Eto Sanso), CH4 (99.9%, Nippon Sanso), andC6F5Cl (Kishida Kagaku, 95%). These reagentswere used without further purification.

trapped by using charged-particle collector
grids. Therefore, only neutral He(23S) atoms
can arrive at the reaction zone as He active
species. A small amount of Ar gas was added to
the He flow 10 cm downstream from the centerof microwave discharge. The positive
Ar+(2P1/2,3/2) ion was produced by the He(23S)/Ar,
Penning ionization.

2.2
Flowing-afterglow
experimental procedure

He(23S) + Ar → Ar+(2P1/2,3/2) + He + e-.
(k2 = 7.04 × 10-11 cm3 s-1 [Ref. 8])

apparatusandTwo-types of flowing-afterglow experiments
were carried out for the Ar+(2P1/2,3/2) reactions.
One is an Ar afterglow experiment shown in
Fig. 1(a), whereas the other is a He afterglow
experiment shown in Fig. 1(b).
In the Ar afterglow experiment, such Ar
active species as metastable Ar(3P0,2) atoms
and Ar+ ions were generated by a microwave
discharge of Ar gas at the output power of 80 W,
and the C6F5Cl gas was introduced from thesecond gas inlet placed 20 cm downstream fromthe center of microwave discharge. Effects ofcharged particles were examined by using apair of charged-particle collector grids placed
between the discharge section and the reaction
zone. The partial pressures in the reaction zone
were 0.18–1.0 Torr (1 Torr = 133.33 Pa) for Ar
and 3–5 mTorr for C6F5Cl.
In the He afterglow experiment such He
active species as He(23S), He+, and He2+ weregenerated by a microwave discharge of highpurity He gas at the output power of 70 W. He+
and He2+ ions in the discharge flow were(a)N2

C6H5ClAr

To pump
Mass flow meter
Microwave
cavityQuartzwindow

Grids

Variable gate valve

(b)
Ar,N2

He

C6H5ClTo pump
Mass flow meter
Microwave
cavityGrids

Quartzwindow

Variable gate valve

Fig. 1. (a) Ar and (b) He flowing-afterglow
apparatuses for the study on theAr+(2P1/2,3/2)/C6F5Cl- ion-ion recombination
reaction. N2 was added as a filter gas of theAr+(2P1/2) component.

(2)

An electron attachment gas, C6F5Cl, was addedfrom the second gas inlet, where C6F5Cl- ion
was formed by a fast non-dissociative electron
attachment.
C6F5Cl + e- → C6F5Cl-.
(k3 = 1.0 × 10-7 cm3 s-1 [Ref. 9])(3)

Kr+(2P1/2,3/2) and Xe+(2P1/2,3/2) reactions werecarried out using similar He afterglow
apparatus. In these cases, Kr+(2P1/2,3/2) andXe+(2P1/2,3/2) ions were formed by He(23S)/Kr
Penning
ionization,andHe(23S)/Xe
respectively.
He(23S) + Kr → Kr+(2P1/2,3/2) + He + e-.
(k4 = 9.94 × 10-11 cm3 s-1 [Ref. 8])(4)

He(23S) + Xe → Xe+(2P1/2,3/2) + He + e-.
(k5 = 1.24 × 10-10 cm3 s-1 [Ref. 8])(5)The partial pressures in the reaction zone were
1.0 Torr (1 Torr = 133.33 Pa) for He, 5–40
mTorr for Rg (Rg = Ar, Kr, and Xe), and 3–5
mTorr for C6F5Cl. The greatest advantage ofthe He afterglow experiment is that we cansave expensive rare gases, Kr and Xe for the
Kr+(2P1/2,3/2) and Xe+(2P1/2,3/2) reactions.
When the effects of incident spin-orbit statesin Ar+(2P1/2,3/2), Kr+(2P1/2,3/2), and Xe+(2P1/2,3/2)
were examined, one of the spin-orbit states was
isolated before reaching the second gas inlet.
For the isolation of Ar+(2P3/2), Kr+(2P1/2),
Xe+(2P1/2), and Xe+(2P3/2), N2, O2, C2H2, and CH4
were used as filter gases, respectively, because
the quenching rate constants of the 2P1/2 and2P3/2 states are different at least one order ofmagnitude.
(6a)Ar+(2P1/2) + N2 → Ar+(2P3/2) + N2,(k6a = 3.2 × 10-11 cm3 s-1 [Ref. 10])Ar+(2P1/2) + N2 → N2+ + Ar,(6b)(k6b = 3.8 × 10-11 cm3 s-1 [Ref. 10])

令和 5 年度

九州大学大学院総合理工学報告

Ar+(2P3/2) + N2 → N2+ + Ar.
(6c)(k6c = 3.7 × 10-12 cm3 s-1 [Ref. 10])(7a)Kr+(2P1/2) + O2 → no products,(k7a ≤ 1 × 10-12 cm3 s-1 [Ref. 11])
Kr+(2P3/2) + O2 → O2+ + Kr.
(7b)(k7b = 4.7 × 10-11 cm3 s-1 [Ref. 11])

第 45 巻

第1号(a) Ar/C6F5Cl (0.18 Torr)(b) Ar/C6F5Cl (0.42 Torr)(9a)
Xe+(2P3/2) + CH4 → CH4+ + Xe,(k9a = 9.0 × 10-10 cm3 s-1 [Ref. 11])
Xe+(2P1/2) + CH4 → no products.
(9b)(k9b ≤ 1 × 10-12 cm3 s-1 [Ref. 11])
These filter gases were injected from the firstgas inlet, as shown in Figs (1a) and (1b) for thecase of N2 in the Ar+(2P1/2,3/2)/C6F5Cl- reaction.
The partial pressures of the filter gases were
10–200 mTorr.
The emission spectra, observed around the
C6F5Cl gas inlet, were dispersed in the 120–840
nm region with McPherson 218 and Spex
1250M monochromators. Photon signals from acooled photomultiplier were analyzed with amicrocomputer.
We used ionization potentials of Ar, Kr, Xe,
and C6F5Cl, electron affinity of C6F5Cl,
dissociation energy of D(C6F5–Cl), excitationenergies of RgCl* reported in Refs. 12–18 forthe calculations of energetics in each reaction.

3.

Results and Discussion

3.1 Formation of ArCl* excimer from theAr+(2P1/2,3/2)/C6F5Cl- reaction in the Ar and He
afterglow
Figures 2(a)–2(d) show emission spectra of
C6F5Cl in an Ar flowing afterglow at various Ar
gas pressures. At the lowest Ar pressure of 0.18
Torr, very weak unidentified atomic lines areobserved. At higher Ar gas pressures of 0.42–
1.0 Torr, three transitions of ArCl* excimer andCl* lines are identified in the 130–210 nm
region. The intensities of ArCl* and Cl*
increase with increasing the Ar pressure from
0.42 Torr to 0.68 Torr, and then decrease withfurther increasing Ar pressure from 0.68 Torr
to 1.0 Torr. ArCl* excimer bands, on which
present work focuses, consists of the strong
B(1/2)–X(1/2) transition in the 160–180 nm
region, the weak D(1/2)–X(1/2) transition in the

B-X

ArCl (B-X)
ArCl (D-X)
ArCl (C-A)(c) Ar/C6F5Cl (0.68 Torr)Cl*

ArCl (B-X)
ArCl (D-X)(8a)
Xe+(2P1/2) + C2H2 → C2H2+ + Xe,(k8a = 3.5 × 10-11 cm3 s-1 [Ref. 11])
Xe+(2P3/2) + C2H2 → C2H2+ + Xe.
(8b)(k8b = 5.0 × 10-10 cm3 s-1 [Ref. 11])15

ArCl (C-A)(d) Ar/C6F5Cl (1.0 Torr)

120

140

160

180

200

220

Wavelength (nm)Fig. 2. Emission spectra resulting from theAr+(2P1/2,3/2)/C6F5Cl- reaction in the 110–220
nm region at various Ar gas pressures.
140–173 nm region, and the weak broad C(3/2)–
A(3/2) transition in the 180–207 nm region.
Since the B, C, and D states of RgX* arestrongly bound, whereas the X and A states of
RgX* are repulsive,16-18) continuous bands
without vibrational structures are observed for
the ArCl(B–X, D–X, C–A) bound-freetransitions.
Possible excitation sources of ArCl*emissions are metastable Ar(3P2) and Ar(3P0)
atoms and Ar+(2P3/2) and Ar+(2P1/2) ions. Theenergetics for the formation of ArCl(B,C,D)
and
from
the
Ar(3P0,2)/C6F5Cl
Ar+(2P1/2,3/2)/C6F5Cl- reaction is as follows:
Ar(3P2) + C6F5Cl→ ArCl(B) + C6F5 + 0.58 eV,→ ArCl(C) + C6F5 + 0.48 eV,→ ArCl(D) + C6F5 + 0.28 eV.

(10a)
(10b)
(10c)

Ar(3P0) + C6F5Cl→ ArCl(B) + C6F5 + 0.75 eV,→ ArCl(C) + C6F5 + 0.65 eV,→ ArCl(D) + C6F5 + 0.45 eV.

(11a)
(11b)
(11c)

Ar+(2P3/2) + C6F5Cl→ ArCl(B) + C6F5 + 4.04 eV,→ ArCl(C) + C6F5 + 3.94 eV,→ ArCl(D) + C6F5 + 3.74 eV.

(12a)
(12b)
(12c)

Ar+(2P1/2) + C6F5Cl→ ArCl(B) + C6F5 + 4.22 eV,→ ArCl(C) + C6F5 + 4.12 eV,→ ArCl(D) + C6F5 + 3.92 eV.

(13a)
(13b)
(13c)

Based on energetics, both metastable Ar(3P0,2)
atoms and Ar+(2P3/2,1/2) ions can be excitation

Spin-orbit state selectivity for RgCl(B,C,D) excimers produced from recombination reactions of Rg+ with C6F5Cl-

16

sources of ArCl*. Figures 3(a) and 3(b) show
emission spectra at an Ar pressure of 0.68 Torr
without and after ion trapping using ion
collector grids, respectively. ArCl* and Cl*
emissions disappear almost completely in Fig.
3(b), indicating that only charged Ar+(2P3/2,1/2)
ions take part in the formation of ArCl* and Cl*
at 0.68 Torr.
In order to further confirm the excitation
source of ArCl* emission in the Ar flowing
afterglow, the Ar pressure dependence ofArCl(B–X) emission was compared with thoseof N2(C–B) emission due to the Ar(3P0,2)/N2
reaction19,20) and ArF(B–X) emission due to theAr+(2P1/2,3/2)/SF6- reaction (Fig. 4).1,2)
Ar(3P0,2) + N2 → N2(C) + Ar.
Ar+(2P1/2,3/2) + SF6- → ArF(B) + SF5.

(14)
(15)

The ArCl(B–X) and ArF(B–X) bands by theAr+(2P1/2,3/2) reaction appeared at an Ar
pressure of ~0.2 Torr with a single intensity
peak at ~0.65 Torr, while the N2(C–B) band by
the Ar(3P0,2)/N2 reaction appeared at a lower Ar
pressure of ~0.05 Torr with two intensity peaks
at 0.15 and 0.7 Torr. A similar Ar pressure
dependence between ArCl(B–X) and ArF(B–X)
emissions suggests that ArCl(B) excimer is

N2 pressure(a) 0 mTorr

Cl*

B-X

ArCl

D-X
C-A

(b) 0 mTorr (grid on)(c) 17 mTorr

B-X
D-X

(d) (a) – (c)120

D-X B-X
140

160

180

200

220

Wavelength (nm)Fig. 3. Emission spectra resulting from the(a) Ar+(2P1/2,3/2)/C6F5Cl- reaction in the Ar
afterglow, (b) ion-collection in spectrum (a),(c) by the addition of 17 mTorr of N2, and (d)Ar+(2P1/2)/C6F5Cl- reaction. Spectrum (d) was
obtained by subtracting spectrum (c) fromspectrum (a).

Ar/C6F5Cl

1.0

Ar/SF6
Ar/N2

0.5

0.0

0.00

0.25

0.50

0.75

1.00

PAr (Torr)
Fig. 4. Dependence of emission intensities ofArCl(B–X) band from the Ar+/C6F5Clreaction, ArF(B–X) band from the Ar+/SF6reaction, and N2(C–B) band from theAr(3P0,2)/N2 reaction in the Ar flowing
afterglow.
formed by the Ar+(2P1/2,3/2) reaction. An
important finding in this work is that productchannels leading to ArCl(B,C,D) excimers,
processes (10) and (11), are closed in theAr(3P0,2)/C6F5Cl reaction, even though they areenergetically allowed.
Figure A1 in Appendix shows effects of N2
addition on the emission spectra of ArCl*
resulting from the Ar+(2P1/2,3/2)/C6F5Cl- reaction.
With increasing the N2 pressure, the[Ar+(2P3/2)]/[Ar+(2P1/2)] ratio is expected to beenhanced. Without addition of N2 (Fig. A1(a)),
the weak ArCl(D–X) band appears as ashoulder band of the main ArCl(B–X) band, andthe weak broad ArCl(C–A) band is observed in
the longer wavelength region of the ArCl(B–X)
band. With increasing the partial pressure ofN2 from 21 mTorr to 93 mTorr (Fig. A1(b)–1(e)),
the intensity of ArCl(D–X) band decreases
more rapidly than those of ArCl(B–X) andArCl(C–A) bands, and the ArCl(D–X) band
almost disappears at the highest N2 pressure of
140 mTorr (Fig. A1(f)). This shows that theArCl(D–X) band is produced from theAr+(2P1/2)/C6F5Cl- reaction, whereas ArCl(B–X)
and ArCl(C–A) bands arise from theAr+(2P3/2)/C6F5Cl- reaction.
A similar disappearance of the ArCl(D–X)
band by the N2 addition is found in theAr+(2P1/2,3/2)/C6F5Cl- reaction in the He令和 5 年度

九州大学大学院総合理工学報告第 45 巻

第1号

17

afterglow (Fig. A2(a)–2(d) in Appendix). With
increasing the N2 pressure, ArCl(D–X) banddecreases more rapidly than those of ArCl(B–X,C–A) bands, and it nearly disappears at N2
pressure of 19 mTorr. From the intensity ratio
between the ArCl(B–X) and ArCl(C–A) bands
in the Ar and He afterglow, the branching ratioof ArCl(B) and ArCl(C) in processes (12a) and(12b) was estimated to be 0.74:0.26,
respectively.
Figure 3(c) shows emission spectrum of
C6F5Cl in the Ar flowing afterglow after
addition of 17 mTorr of N2. ArCl(B–X,C–A,D–
X) emissions reduced their intensities incomparison with those in Fig. 3(a) obtained
without N2 addition. Decay rate of Ar+(2P1/2) isabout 20 times faster than that of Ar+(2P3/2) by
the N2 addition. Thus, we examined thecontribution of the Ar+(2P1/2) reaction by
assuming that ArCl* emission resulting only
from the Ar+(2P1/2)/C6F5Cl- reaction isattenuated by the addition of a small amount of
N2 (17 mTorr). Figure 3(d) shows emission
spectrum of the Ar+(2P1/2)/C6F5Cl- reaction
obtained by subtracting spectrum (c) fromspectrum (a). In Fig. 3(d), weak ArCl(B-X) andArCl(D–X) bands are observed, and theintensity of the ArCl(D–X) band is stronger
than that of the ArCl(B–X) one. From theintensity ratio of the two band systems, thebranching ratio of ArCl(B) and ArCl(D) inprocesses (13a) and (13c) was estimated to be
0.35:0.65, respectively.

and (17c) were evaluated to be 0.71:0.29 and0.05:0.95, respectively.

3.2 Formation of KrCl* excimer from theKr+(2P1/2,3/2)/C6F5Cl- reaction in the He
afterglow

Fig. 5. Emission spectra resulting from the
Kr+/C6F5Cl- reaction in the 150–280 nm or
170–230 nm region. (a) without O2 addition, (b)50 mTorr O2 addition, (c) 100 mTorr O2
addition, (d) 200 mTorr O2 addition.

Figure 5(a) shows emission spectrum
resulting from the Kr+(2P1/2,3/2)/C6F5Cl- reactionin the He afterglow. The strong KrCl(B–X)
band, the very weak KrCl(D–X) band, and theweak broad KrCl(C–A) band are identified in
the 160–225, 160–200, and 225–275 nm region,
respectively. Figures 5(b) and 5(c), respectively,
show emission spectra obtained by addition of
O2 at partial pressures of 50 and 100 mTorr toenhance the [Kr+(2P1/2)]/[Kr+(2P3/2)] ratio. With
increasing the partial pressure of O2, KrCl(D–X)/KrCl(B–X) intensity ratio increases. By theaddition of a sufficient amount of O2 (~200mTorr), the KrCl(D–X)/KrCl(B–X) intensity
ratio further increases and becomes constant,
as shown in Fig. 5(d). Based on theseexperiments, the branching ratio of KrCl(B)and KrCl(C) in processes (16a) and (16b), andthat of KrCl(B) and KrCl(D) in processes (17a)Kr+(2P3/2) + C6F5Cl→ KrCl(B) + C6F5 + 3.67 eV,→ KrCl(C) + C6F5 + 3.67 eV,→ KrCl(D) + C6F5 + 3.05 eV.

(16a)
(16b)
(16c)

Kr+(2P1/2) + C6F5Cl→ KrCl(B) + C6F5 + 4.34 eV,→ KrCl(C) + C6F5 + 4.34 eV,→ KrCl(D) + C6F5 + 3.72 eV.

(17a)
(17b)
(17c)

(a)
O2 pressure(a) 0 mTorr

KrCl

B-X
D-X

C-A

×10

(b)
(b) 50 mTorr

×10

(c)

(c) 100 mTorr ×10

150

200

250

280

Wavelength (nm)
(d)

D-X

(d) 200 mTorr

KrCl
B-X

170

180

190

200

210

220

Wavelength (nm)3.3 Formation of XeCl* excimer from theXe+(2P1/2,3/2)/C6F5Cl- reaction in the He
afterglow
Figure 6(a) shows emission spectrum
resulting from the Xe+(2P1/2,3/2)/C6F5Cl- reactionin the He afterglow. XeCl* excimer bands
consist of the strong XeCl(B–X) band in the
250–320 nm region, the very weak XeCl(D–X)
band in the 200–240 nm region, and the weakbroad XeCl(C–A) band in the 320–450 nm
region. Figures 6(b) and 6(c) show emission
spectra obtained by selecting one-spin-orbit
component using C2H2 or CH4 filter gases,
respectively. In the Xe+(2P1/2)/C6F5Cl- reaction
shown in Fig. 6(b), the XeCl(B–X) band greatly
reduces its intensity by removal of the Xe+(2P3/2)

18

Spin-orbit state selectivity for RgCl(B,C,D) excimers produced from recombination reactions of Rg+ with C6F5Cl(a) Without filter gas(b) C2H2 50 mTorr
D-X(b)4 100 mTorr(c) CH

B-X

B-X

Wavelength (nm)Fig. 6. Emission spectra resulting from the
Xe+/C6F5Cl- reaction in the 200–450 nm
region. (a) Xe+(2P1/2,3/2)/C6F5Cl- reaction(b)
without
additionoffiltergas,
Xe+(2P1/2)/C6F5Cl- reaction by addition of 50
mTorr C2H2, (c) Xe+(2P3/2)/C6F5Cl- reaction byaddition of 100 mTorr CH4.
component, whereas the XeCl(D–X) bandremains its intensity. On the other hand, in theXe+(2P3/2)/C6F5Cl- reaction shown in Fig. 6(c),XeCl(B–X) and XeCl(C–A) bands remain theirintensities, whereas the XeCl(D–X) band
disappears. The branching ratio of XeCl(B) and
XeCl(C) in processes (18a) and (18b) and that ofXeCl(B) and XeCl(D) in processes (19a) and(19c) were evaluated to be 0.70:0.30 and
0.24:0.76, respectively.
Xe+(2P3/2) + C6F5Cl→ XeCl(B) + C6F5 + 3.15 eV,→ XeCl(C) + C6F5 + 3.08 eV,→ XeCl(D) + C6F5 + 1.80 eV.

(18a)
(18b)
(18c)

Xe+(2P1/2) + C6F5Cl→ XeCl(B) + C6F5 + 4.46 eV,→ XeCl(C) + C6F5 + 4.71 eV,→ XeCl(D) + C6F5 + 3.11 eV.

(19a)
(19b)
(19c)

3.4 Branching ratios of RgX(B,C,D) excimers
in the ion-ion recombination reactions andchemiluminescent reactions
In Table 1 are summarized the branchingratios of RgX(B,C,D) excimers in theandRg+(2P3/2)/C6F5ClRg+(2P1/2)/C6F5Clreactions. For comparison, corresponding datareactions
and
for
the
Rg+/SF6chemiluminescent reactions of metastable
Rg(3P0,2) atoms with diatomic and polyatomic
halides RX are also given.

The initial formation ratio of two spin-orbit
components of Kr+ and Xe+, [2P1/2]/[2P3/2], in the
Penning ionization (4) and (5) was estimated tobe 0.56 for Kr+ and 0.49 for Xe+ from theanalysis of Penning ionization electron
spectra.21) We found previously that RgF(B–X)
emissions are formed highly selectively by theRg+(2P3/2)/SF6- reactions, whereas RgF(D–X)
emissions preferentially results from theRg+(2P1/2)/SF6- reactions for Rg = Kr and Xe.2)
Therefore, the [Rg+(2P1/2)]/[Rg+(2P3/2)] ratios canbe estimated by using intensity ratios of
RgF(D–X)/RgF(B–X) excimers resulting fromspin-orbit state selective Rg+(2P1/2,3/2)/SF6reactions, assuming that no significant
difference exists between the rate constant for
the formation of RgF(D) from the Rg+(2P1/2)/SF6reaction and that of RgF(B) from theRg+(2P3/2)/SF6- reaction. We found that the
RgF(B–X) emission is much stronger than thatofRgF(D–X)
emissions,asreportedpreviously.2) It was therefore concluded thatthe lower Rg+(2P3/2) state is major component in
the present experiments, although a small
amount of upper Rg+(2P1/2) state is involved in
all cases.
It is clear that the B and D states are formedby the Rg+(2P1/2)/C6F5Cl- reactions with the Dstate being strongly favored, whereas the B andC state are produced by the Rg+(2P3/2)/C6F5Clreactions with the branching ratio of about 7:3,
respectively in all cases. The Γ(D) values for theandXe+(2P1/2)/C6F5ClAr+(2P1/2)/C6F5Clreactions, 0.65 and 0.76, respectively, aresmaller than that for the Kr+(2P1/2)/C6F5Clreaction, 0.95. The Γ(D) value for the
Kr+(2P1/2)/C6F5Cl- reaction, 0.95, is the same asthat for the Kr+(2P1/2)/SF6- reaction, whereas
the Γ(D) value for the Xe+(2P1/2)/C6F5Clreaction, 0.76, is smaller than that for theXe+(2P1/2)/SF6- reaction, 0.94.
In the chemiluminescent reactions ofmetastable Ar(3P0,2) and Kr(3P0,2) atoms withhalides RX, spin-orbit selectivity is also found.
In these cases, Ar(3P2) and Kr(3P2) reactions
give only B and C states, whereas mixtures of
B and D states are formed in the Ar(3P0) andKr(3P0) reactions. The Γ(D) values in theAr(3P0) and Kr(3P0) reactions range from 0.23 to
0.73, which are about the same or smaller thanthose obtained in the Rg+(2P1/2)/C6F5Clreactions (0.65–0.95). It should be noted that asignificant difference is observed in the spinorbit selectivity between the Xe(3P0)/RX andthe Xe+(2P1/2)/C6F5Cl- reactions. In strong
contrast to the Ar(3P0) and Kr(3P0) reactions,令和 5 年度

九州大学大学院総合理工学報告第 45 巻

第1号

19

Table 1. Branching ratios of RgX(B,C,D) excimers in ion-ion recombination reactions andchemiluminescent (CL) reactions.
Ion-ion reactions
Ar+(2P1/2)/C6F5ClAr+(2P3/2)/C6F5ClKr+(2P1/2)/C6F5ClKr+(2P3/2)/C6F5ClXe+(2P1/2)/C6F5ClXe+(2P3/2)/C6F5Cl-

Γ(B)
This
work
This
work
This
work
This
work
This
work
This
work

0.35
0.74

0.71

Ref. 2

0.05-

Ref. 20.62

Xe ( P1/2)/SF6-

Ref. 2

0.06

Xe+(2P3/2)/SF6-

Ref. 20.68+ 2

CL Reaction

0.65

Ar(3P0)/Cl2

0.95
0.29

0.24
0.70

Γ(D)

0.26

0.05

Kr+(2P1/2)/SF6Kr+(2P3/2)/SF6

Γ(C)

0.76
0.30
0.95
0.38
0.94
0.32

Γ(B)

Γ(C)

Γ(D)

Ref. 5

0.52

0.13

0.35

Ar(3P2)/Cl2

Ref. 50.70

0.30

Ar(3P0)/SOCl2

Ref. 50.40

0.09

Ar(3P2)/SOCl2

Ref. 5

0.69

0.31

Ar(3P0)/PCl3

Ref. 5

0.23

0.04

Ar(3P2)/PCl3

Ref. 5

0.27

0.73

Ar(3P0)/CCl4

Ref. 50.26

0.08

Ar(3P2)/CCl4

Ref. 50.33

0.67

Ar( P0)/F2

Ref. 50.49

0.28

Ar(3P2)/F2

Ref. 50.50

0.50

Kr(3P0)/Cl2

Ref. 6

0.42

Kr(3P2)/Cl2

Ref. 6

0.52

Kr(3P0)/SOCl2

Ref. 6

0.46

Kr( P2)/SOCl2

Ref. 6

0.60

Kr(3P0)/PCl3

Ref. 8

1.00

Kr(3P2)/PCl3

Ref. 6

0.33

Kr(3P0)/CCl4

Ref. 6

0.50

Kr(3P2)/CCl4

Ref. 80.40

3

Xe( P0)/F2

Ref. 7≥0.90

Xe(3P2)/F2

Ref. 71.00 (B + C)

Xe(3P0)/Br2a)

Ref. 7≥0.75

Xe( P2)/Br2

Ref. 71.00 (B + C)

Xe(3P0)/Cl2

Ref. 71.00 (B + C)

Xe(3P2)/Cl2

Ref. 71.00 (B + C)

Xe(3P0)/HCl

Ref. 71.00 (B + C)

Xe(3P2)/HCl

Ref. 71.00 (B + C)

Xe( P0)/PCl3

Ref. 71.00 (B + C)

Xe(3P2)/PCl3

Ref. 71.00 (B + C)

Xe(3P0)/CF3Cl

Ref. 71.00 (B + C)

Xe(3P2)/CF3Cl

Ref. 71.00 (B + C)

3

3

3

3

a) From peak intensity.

Ar(3P0) and Kr(3P0) reactions,

0.51

0.73

0.66
0.23
0.58

0.48
0.54
0.40
0.67
0.50
0.60
≤0.10
≤0.25

20

Spin-orbit state selectivity for RgCl(B,C,D) excimers produced from recombination reactions of Rg+ with C6F5Cl-

the Γ(D) values in the Xe(3P0)/RX reactions are
zero except for F2 (≤0.10) and Br2 (≤0.25). The
Γ(B) + Γ(C) values in the Xe(3P2)/RX reactions
are 1.00 for all reagents, as in the cases of theAr(3P2) and Kr(3P2) reactions and theXe+(2P3/2)/C6F5Cl- reaction.
3.3 Reaction dynamics for the formation ofRgCl(B,C,D) excimers in the reactions of
Rg+(2P1/2,3/2) with C6F5ClThe formation of RgCl* excimers from the
Rg+/C6F5Cl- reactions must proceed throughthe [Rg+–Cl-–C6F5] intermediates.
Rg+ + C6F5Cl→ [Rg+–Cl-–C6F5] → RgCl* + C6F5.

(20)

The formation dynamics of RgX* excimers fromthe Rg(3P0,2)/X2 reaction using a correlation
diagram is shown in Fig. A3 (Appendix), where
RgX* excimers are formed through Rg+(2P1/2,3/2)+ X2- ion-pairs intermediates. It is known thatchanging the designation of the states to Cs
geometry for RX- molecules with A' or A"
symmetry does not alter the broadinterpretation for X2- with higher symmetry.5-7)
Figure 7 shows the schematic potential
diagramofthe
Rg+(2P1/2,3/2)/C6F5Clrecombination
process,
where
the
Ω
designation given in Fig. A3 remains for theRg(3P0,2,3P1) + C6F5Cl, Rg+(2P1/2,3/2) + C6F5Cl-,
and RgCl(B,C,D) + C6F5 systems. The RgCl(D)state correlates to the Rg+(2P1/2) + Cl- ion pair,while the RgCl(B,C) states correlate to theRg+(2P3/2) + Cl- ion pair based upon ab initio
calculations.16-18)
There are quasi continuous Rg + C6F5Cl*(excited states) product channels below theV[Rg+,C6F5Cl-] ion-pair potentials for a
relatively large molecule such as C6F5Cl. Here,
excited states of C6F5Cl involve superexcitedstates above the first ionization potential of
9.72 eV. In addition to the Rg + C6F5Cl* productchannels, a number of Rg**(Rydberg states) +C6F5Cl potentials are present above theRg(3P0,2) + C6F5Cl potentials as productchannels, because the potential energies of
Rg+(2P3/2) + C6F5Cl- are higher than those ofRg(3P0) + C6F5Cl by 1.9−3.3 eV. They are also
shown by hatched lines in Fig. 7. In theAr+(2P1/2,3/2)/C6F5Cl-, Kr+(2P1/2,3/2)/C6F5Cl-, andXe+(2P1/2,3/2)/C6F5Cl- reactions, the following
states exist as candidates for Rg** and some ofthem can interact with the entranceV[Rg+(2P1/2,3/2),C6F5Cl-] ion-pair potentials:
total 59 4s, 4p, 3d, 5s, 5p, 4d, 6s, and 4f states for
Ar**, 51 5s, 5p, 4d, 6s, 6p, 5d, 7s, and 4f statesfor Kr**, and 48 6s, 6p, 5d, 7s, 7p, 6d, 8s, and 4f
states for Xe**. As shown in Table 1, most ofRg(3P0,2)/RX reactions give RgX* excimers via

Potential energy

Rg+(2P1/2) + C6F5Cl-

Rg+(2P3/2) + C6F5ClRg** + C6F5Cl
0-

1,0+

Rg(3P0) + C6F5Cl
2,1,0-

Rg(3P1) + C6F5Cl

Rg(3P2) + C6F5Cl
2,1
Rg + C6F5Cl*

0

Rg + C6F5Cl
R(Rg― C6F5Cl)

Fig. 7. Correlation diagram of the diabatic potentials for theRg(3P0,2)/C6F5Cl and Rg+(2P1/2,3/2)/C6F5Cl- reactions. The stateswith Rg+(2P1/2) ion-core configuration are shown by dashed lines.
The dark circles show positions of strong interactions of the diabatic
potentials. Ω values shown in Fig. A3 for the Rg(3P0,2)/X2 andRg+(2P1/2,3/2)/X2- reactions in collinear geometry are used.

令和 5 年度

九州大学大学院総合理工学報告[Rg+(2P1/2,3/2),RX-] ion-pair intermediates. In
the Xe**(6p,6p′,7p)/RX reactions,22,23) XeX*
excimer formation via V[Xe+(2P1/2,3/2),RX-] ionpair potentials has also been observed,
indicating that higher energy entranceV[Xe**(6p,6p′,7p),RX] potentials really couple
with the V[Xe+(2P1/2,3/2),RX-] ion-pair potentials.
If the attractive ion-pair potentials strongly
couple with some of these V[Rg,C6F5Cl*] orV[Rg**,C6F5Cl] potentials, this coupling
diverts trajectories from the ion-pair potential
to the V[Rg,C6F5Cl*] or V[Rg**,C6F5Cl]
potentials. The preferential formation ofRgCl(D) from the Rg+(2P1/2)/C6F5Cl- reactions
and the selective formation of RgF(B,C) fromthe Rg+(2P3/2)/C6F5Cl- reactions imply that
trajectorylossbyinteractions
with
V[Rg,C6F5Cl*] or V[Rg**,C6F5Cl] potentials is
small, so that the RgCl* excimers could beformed through diabatic pathways predictedfrom the potential diagram.
Rg+(2P1/2) + C6F5Cl- → [Rg+(2P1/2),Cl-] + C6F5,↓
RgCl(D).
(21a)
Rg+(2P3/2) + C6F5Cl- → [Rg+(2P3/2),Cl-] + C6F5,↓
RgCl(B,C).
(21b)
On the basis of this finding, the electronic
configuration of rare gas ion is conserved wellduring the Rg+(2P1/2,3/2)/C6F5Cl- reactions.
The formation of a small amount of RgCl(B)from the Rg+(2P1/2)/C6F5Cl- reaction suggeststhat the conservation of ion configuration ispartially broken. One possible route for theformationofRgCl(B)fromthe
Rg+(2P1/2)/C6F5Cl- reaction shown in Fig. 7 isthe first curve crossing between the Ω = 0entrance V[Rg+(2P1/2),C6F5Cl-] potential and theΩ = 0- potential arising from Rg(3P0) + C6F5Cl
followed by the second curve crossing between
the Ω = 0- potential from Rg(3P0) + C6F5Cl andthe Ω = 0- potential arising from Rg+(2P3/2) +C6F5Cl-.
Rg+(2P1/2) + C6F5Cl- → [Rg+(2P1/2),C6F5Cl-],↓[Rg(3P0),C6F5Cl],↓[Rg+(2P3/2),C6F5Cl-],↓
RgCl(B) + C6F5. (22)Other possibilities are similar interactions

第 45 巻第1号

21

betweenthe
entrance
V[Rg+(2P1/2),RX-]
potential and some V[Rg**,RX] potential
followed by interaction between V[Rg**,RX]and V[Rg+(2P3/2),RX-] potentials.
ThesmallerΓ(D)valuesintheandXe+(2P1/2)/C6F5ClAr+(2P1/2)/C6F5Clreactions than that in the Kr+(2P1/2)/C6F5Clreaction suggest that conversion of ion-core
configuration via curve crossings occurs withhigher probability in the former reactions.
The spin-orbit state selectivity for theexcimer formation in the reactions ofmetastable Rg(3P0,2) atoms with RX has beenstudied by Setser and his co-workers.5-7) They
discussed the electronic state selectivity of
RgX* excimer in the Rg(3P0,2) reactions by both
the J state and the ion core. As an example,
Figure A3 in Appendix shows a schematic
diagram of the RgX* formation from theRg(3P0,2)/X2 reactions obtained by assuming acollinear approach. A similar potential diagram
will be applicable to the formation of RgX* fromthe other Rg(3P0,2)/RX reactions with a lower
molecular symmetry. The formation of RgX* by
the Rg(3P0,2)/X2 reactions proceeds throughharpoon-type reactions via [Rg+,X2 ] ion-pairintermediates. The metastable Rg(3P0) andRg(3P2) atoms have Rg+(2P1/2) and Rg+(2P3/2) ion
cores,
respectively.
Iftheion-coreconfigurations of Rg(3P0) and Rg(3P2) areconserved, the Rg(3P0) atoms should yield theRgX(D) state through an [Rg+(2P1/2),X2 ]intermediate, whereas the RgX(B,C) states
would be formed through an [Rg+(2P3/2),X2 ]intermediate.
Rg(3P0) + X2 → [Rg+(2P1/2),X2-],↓
RgX(D) + X.

(23a)

Rg(3P2) + X2 → [Rg+(2P2/2),X2-],↓
RgX(B,C) + X.

(23b)

Thus, the formation of D state from theRg(3P0)/X2 reactions and the B and C statesfrom the Rg(3P2)/X2 reactions has been
explained by the conservation of ion-core2
configurations.
The formation of B from theRg(3P0) reactions, which does not conserve theion-core configuration, was attributed to acrossing between the Ω = 0- entranceV[Rg(3P0),X2] potential and the Ω = 0V[Rg+(2P3/2),X2-] potential. In the Rg(3P0)/X2
reactions, the crossing between the entrance Ω= 0- potential and the outer Ω = 0-

22Spin-orbit state selectivity for RgCl(B,C,D) excimers produced from recombination reactions of Rg+ with C6F5Cl-

V[Rg+(2P3/2),X2-] potential occurs before theformation of the [Rg+(2P1/2),X2-] intermediate.
Therefore, for the formation of RgX(D) state,
trajectories via V[Rg(3P0),X2] potential must
pass through the outer crossing with theV[Rg+(2P3/2),X2 ] potential and continue to theinner V[Rg+(2P1/2),X2 ] potential.
In general, this diagram can also be applied
to RX reagents as shown in Fig 7 for C6F5Cl. It
should be noted that such an outer crossing is
unnecessaryfortheformationofintermediateinthe[Rg+(2P1/2),RX-]
Rg+(2P1/2)/RX- ionic­recombination reactions.
Therefore, loss of initial trajectories by outercrossing is absent, so that a high propensity forthe formation of RgCl(D) can be achieved in the
Rg+(2P1/2)/C6F5Cl- reactions in comparison withthat in the Rg(3P0)/RX reaction. Higher
propensity of RgX*(D) is especially found in theXe+(2P1/2)/C6F5Cl- reaction in comparison withthat in the Xe(3P0)/RX reactions (Table 1). Zonget al.7) attributed the low propensity of RgX*(D)in the Xe(3P0)/RX reactions to a coupling
between the V[Xe(6s' 3P0),RX] and V[Xe(6p),RX]
potentials in the entrance channel, because theemission spectra and the product branchingratios for XeX(B) formation from the reactionsof Xe(3P0) with RX molecules are similar to
those from reactions of Xe(6p) atoms. The
covalent V[Xe(6s' 3P0),RX] and V[Xe(6p),RX]
potentials are rather flat before crossing withstrongly attractive ion-pair V[Xe+(2P1/2),RX-]
potential as reported by Nelson et al.22) The
V[Xe(6p),RX] potentials are located at least
0.13 eV above the V[Xe(6s' 3P0),RX] potential. It
is therefore expected that coupling between theV[Xe(6s' 3P0),RX] and V[Xe(6p),RX] potentials
in the entrance channel is weak at thermalenergy. On the basis of present results, ion
configuration is rather well conserved in theXe+(2P1/2)/C6F5Cl- reaction, even though theentrance V[Xe+(2P1/2),C6F5Cl-] potential cancouple with many V[Xe**,C6F5Cl] potentials
involving V[Xe(6p),C6F5Cl] potential. It istherefore reasonable to assume that the low
propensity of RgX*(D) in the Xe(3P0)/RX
reactions arises from strong coupling of theentrance Ω = 0- (A″) V[Xe(3P0),RX] potential
with outer Ω = 0- (A″) V[Xe+(2P3/2),RX ] potential.
In the Ar(3P0,2)/C6F5Cl reactions, no
ArCl(B,C,D) formation was observed, eventhough they are energetically allowed. One
possibility is the main product channel is
Penning ionization leading to C6F5Cl+, because
the ionization potential of C6F5Cl (9.72 eV) is
lower than energies of Ar(3P2:11.55 eV,

3P0:11.72 eV).

Ar(3P0,2) + C6F5Cl → C6F5Cl+ + Ar + e-. (24)Another possibility is that interactions of theentrance V[Ar(3P0,2),C6F5Cl] potential withmany low lying V[Ar,C6F5Cl*] potentials occur
either directly or via V[Ar+(2P1/2,3/2),C6F5Cl-]
ion-pair potentials with high probability, sothat no trajectories leading to ArCl* remain.
The conservation of ion configuration in theandXe+(2P1/2)/C6F5ClAr+(2P1/2)/C6F5Clreactions were smaller than that in the
Kr+(2P1/2)/C6F5Cl- reaction. This suggests thatinteractions of entrance V[Ar+(2P1/2),C6F5Cl-]
and V[Xe+(2P1/2),C6F5Cl-] potentials with
V[Ar**,C6F5Cl-] and V[Xe**,C6F5Cl-] potentials,
which divert the entrance trajectories, arestronger than that in the case of
Kr+(2P1/2)/C6F5Cl- reaction.

4.

Summary and Conclusion

Spin-orbit state selectivity of RgCl(B,C,D)
excimers in the Rg+(2P1/2,3/2)/C6F5Cl- reactions
was examined by selecting one spin-orbit
component of Rg+(2P1/2,3/2). The RgCl(B,D) ratio
was determined to be 0.35:0.65, 0.05:0.95, and0.24:0.76 in the Ag+(2P1/2), Kr+(2P1/2), andXe+(2P1/2) reactions, whereas the RgCl(B,C)
ratio was estimated to be 0.74:0.26, 0.71:0.29,
and 0.70:0.30 in the Ag+(2P3/2), Kr+(2P3/2), andXe+(2P3/2) reactions, respectively. The highpropensities for the D formation from theRg+(2P1/2)/C6F5Cl- reactions and for the B and C
formation from the Rg+(2P3/2)/C6F5Cl- reactions
could be explained by the conservation of the
Rg+(2P1/2) + Cl- and Rg+(2P3/2) + Cl- charactersfor the formation of RgCl*. A high propensity
for the formation of RgCl(D) in the
Rg+(2P1/2)/C6F5Cl- reactions in comparison withthat in the Rg(3P0)/RX reactions was discussed
by using a correlation diagram between
entrance and exit product channels. In theRg(3P0)/RX reactions, the crossing between theentrance Ω = 0- (A″) potential and the outer Ω= 0- (A″) V[Rg+(2P3/2),RX-] potential occurs
before the formation of the [Rg+(2P1/2),RX-]intermediate. Such a crossing is unnecessaryfortheformationof[Rg+(2P1/2),RX-]intermediate in the ionic­recombination
reactions. Therefore, a high propensity for theformation of RgCl(D) can be achieved in the
Rg+(2P1/2)/C6F5Cl- reactions. The present
results demonstrated the ionic recombination
is better reaction for the selective formation of令和 5 年度

九州大学大学院総合理工学報告

RgX(D) excimers than the chemiluminescent
reactions by the metastable Rg(3P0) atoms.
Acknowledgments
The authors acknowledge Prof. Kenji Furuya
of Kyushu University for his careful reading of
our manuscript. This work has been supportedby the Morino Foundation for molecular science(1992), the Iwatani Naoji Memorial Foundation(1993), and Showa Shell Sekiyu Foundation forenvironmental research (1995).
References
1)
2)
3)
4)
5)
6)
7)
8)
9)

M. Tsuji, M. Furusawa, and Y. Nishimura, Chem.
Phys. Lett., 166, 363 (1990).
M. Tsuji, M. Furusawa, H. Kouno, and Y. Nishimura,
J. Chem. Phys., 94, 4291 (1991).
M. Tsuji, Trends Phys. Chem., 5, 25 (1995).
M. Tsuji, Houshasenkagaku, 62, 18 (1996).
N. Sadeghi, M. Cheaib, and D. W. Setser, J. Chem.
Phys., 90, 219 (1989).
D. Zhong, D. W. Setser, R. Sobczynski, and W.
Gadomski, J. Chem. Phys., 105, 5020 (1992).
D. Zhong and D. W. Setser, Chem. Phys. Lett., 207,555 (1993).
A. L. Schmeltekopf and F. C. Fehsenfeld, J. Chem.
Phys., 53, 2000 (1970).
T. M. Miller and A. A. Viggiano, Phys. Rev. A, 71,
012702 (2005).

第 45 巻第1号

2310) A. B. Rakshit and P. Warneck, J. Chem. Phys., 73,
2673 (1980).
11) K. Giles, N. G. Adams, and D. Smith, J. Phys. B, 22,873 (1983).
12) C. E. Moore, “Atomic Energy Levels,” U.S. GPO,
Washington D.C., Natl. Bur. Stand. (U.S.) Circ. 467(1949).
13) Atomic Spectra Database, NIST Standard Reference
Database, 78, Ver. 5.9. Oct. (2021).
14) Y.-R. Luo, “Bond Dissociation Energies”, in CRC
Handbook of Chemistry and Physics, 81th Ed., CRC
Press, Boca Raton (2000).
15) NIST Chemistry WebBook, NIST Standard Reference
Number69(2022)
Database,https://doi.org/10.18434/T4D303
16) P. J. Hay and T. H. Dunning, J. Chem. Phys., 66, 1306
(1977).
17) T. H. Dunning and P. J. Hay, J. Chem. Phys., 69, 134(1978).
18) P. J. Hay and T. H. Dunning, J. Chem. Phys., 69, 2209
(1978).
19) T. D. Nguyen and N. Sadeghi, Chem. Phys., 79, 41(1983).
20) J. Derouard, T. D. Nguyen, and N. Sadeghi, J. Chem.
Phys., 72, 6698 (1980).
21) C. E. Brion, C. A. McDowell, and W. B. Stewart, J.
Electron Spectrosc., 1, 113 (1972/73).
22) T. O. Nelson, D. W. Setser, and K. Richmann, J. Phys.
Chem., 99, 7482 (1995).
23) V. Alekseev and D. W. Setser, J. Phys. Chem., 100,
5766 (1996).

Appendix

N2 pressure(a) 0 mTorr

Cl*

B-X
D-X

ArCl

B-X

N2 pressure(a) 0 mTorr

C-A

ArCl

D-X
C-A

Cl*

(b) 21 mTorr(b) 5 mTorr(c) 47 mTorr(d) 70 mTorr(c) 14 mTorr(e) 93 mTorr(f) 140 mTorr

120

140

160

180

200

220

(d) 19 mTorr

Wavelength (nm)Fig. A1. Effects of N2 addition to theemission spectra of ArCl* resulting from theAr+(2P1/2,3/2)/C6F5Cl- reaction in the Ar
afterglow.

120

140

160

180

200

220

Wavelength (nm)Fig. A2. Effects of N2 addition to the emission
spectra of ArCl* resulting from theAr+(2P1/2,3/2)/C6F5Cl- reaction in the He
afterglow.

Spin-orbit state selectivity for RgCl(B,C,D) excimers produced from recombination reactions of Rg+ with C6F5Cl-

Rg+(2P3/2) + X2-(2Σu+)

Rg+(2P1/2) + X2-(2Σu+)Potential energy

24

01,0+

Rg(3P0) + X2(1Σg+)
2,1,0-

Rg(3P1) + X2(1Σg+)

Rg(3P2) + X2(1Σg+)2,10Rg + X2
R(Rg―X2)

Fig. A3. Correlation diagram of the diabatic potentials for
the Rg(3P0,2)/X2 and Rg+(2P1/2,3/2)/X2- reactions in collinear
geometry.5) The states with Rg+(2P1/2) ion-core configuration
are shown by dashed lines. The dark circles show positionsof expected strong interactions of the diabatic potentials. The
only Ω = 1/2 components correlating to X(2P3/2) have been
included in the drawing because they are more important
than Ω = 3/2 components.