A variable temperature-selected ion flow drift tube (VT-SIFDT) has been used to measure the mobilities of NH4+(NH3)n clusters drifting in He. The mobilities have been measured for n=0–2 at 298 K, n=0–3 at 200 K, and n=0–5 at 100 K, marking the first mobilities experiments for these clusters below room temperature. The reduced mobilities measured at 298 K are compared to the previous SIFDT results of Krishnamurthy et al. [J. Chem. Phys. 106, 530 (1997)] for n=0–2. While the current results compare quite favorably for n=0–2, there is a discrepancy for n=3 which is addressed by current 100 K and 200 K data where these species are thermally stable. The trends in the mobilities from 100 K to 298 K as a function of E/N and effective temperature reveal that the repulsive part of the He–NH4+(NH3)n interaction potential is sampled predominantly for n=1–5. However, the attractive part of the potential is accessed at the lowest temperatures for He–NH4+.

1.
M.
Krishnamurthy
,
J. A.
de Gouw
,
L. N.
Ding
,
V. M.
Bierbaum
, and
S. R.
Leone
,
J. Chem. Phys.
106
,
530
(
1997
).
2.
E. A. Mason and E. W. McDaniel, Transport Properties of Ions in Gases (Wiley, New York, 1988).
3.
R. A.
Barker
and
D. P.
Ridge
,
J. Chem. Phys.
64
,
4411
(
1976
).
4.
A. A.
Viggiano
and
A. J.
Midey
,
J. Phys. Chem.
104
,
6786
(
2000
).
5.
A. A.
Viggiano
,
S. T.
Arnold
, and
R. A.
Morris
,
Int. Rev. Phys. Chem.
17
,
147
(
1998
).
6.
A. A.
Viggiano
,
R. A.
Morris
,
F.
Dale
,
J. F.
Paulson
,
K.
Giles
,
D.
Smith
, and
T.
Su
,
J. Chem. Phys.
93
,
1149
(
1990
).
7.
A. A.
Viggiano
and
R. A.
Morris
,
J. Phys. Chem.
100
,
19227
(
1996
).
8.
W.
Lindinger
and
D. L.
Albritton
,
J. Chem. Phys.
62
,
3517
(
1975
).
9.
R. G.
Keesee
and
A. W.
Castleman
, Jr.
,
J. Phys. Chem. Ref. Data
15
,
1011
(
1986
).
10.
J. A. de Gouw and S. R. Leone, personal communication.
11.
L. A.
Viehland
,
M. M.
Harrington
, and
E. A.
Mason
,
Chem. Phys.
17
,
433
(
1976
).
12.
L. A.
Viehland
and
E. A.
Mason
,
Chem. Phys. Lett.
83
,
298
(
1981
).
13.
O.
Dopfer
,
S. A.
Nizkorodov
,
M.
Meuwly
,
E. J.
Bieske
, and
J. P.
Maier
,
Chem. Phys. Lett.
260
,
545
(
1996
).
14.
J. P.
Read
and
A. D.
Buckingham
,
Chem. Phys. Lett.
270
,
245
(
1997
).
This content is only available via PDF.
You do not currently have access to this content.