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Phophine is an oblate, near spherical rotor, similar
to ammonia. The off-diagonal centrifugal distortion
term ε causes a splitting between respective
A1 and the A2 levels for
K = 3n, with
n > 0, which increases
rapidly with increasing J and decreasing
K. Tunneling is not important in phosphine.
With respect the the first entry from Oct. 2008,
the spectroscopic parameters have been reevaluated
by
(1) H. S. P. Müller,
2013, J. Quant. Spectrosc. Radiat. Transfer
130, 335.
The main effect occurs for the intensities of
ΔK = 3 transitions. In
addition, some uncertainties have been reassigned.
Pure rotational transition frequencies with
ΔK = 0 were taken
from
(2) G. Cazzoli and C. Puzzarini,
2006, J. Mol. Spectrosc. 239, 64
for J" ≤ 2; those with
J" = 3 were taken
from
(3) S. P. Belov, A. V. Burenin, L. I. Gershtein,
A. F. Krupnov, V. N. Markov, A. V. Maslovsky, and
S. M. Shapin,
1981, J. Mol. Spectrosc. 86, 184.
In addition, higher-J transitions have been
recorded by far-infrared spectroscopy
by
(4) L. Fusina and M. Carlotti,
1988, J. Mol. Spectrosc. 130, 371.
Furthermore, weak K = 3 splitting
transitions and ΔK = 3
transitions have also been measured and used in the fit.
These were reported by
(5) P. B. Davis, R. M. Neumann, S. C. Wofsy, and
W. Klemperer,
1971, J. Chem. Phys. 55, 3564;
(6) F. Y. Chu and T. Oka,
1974, J. Chem. Phys. 60, 4612;
(7) D. A. Helms and W. Gordy,
1977, J. Mol. Spectrosc. 66, 206;
and from
(8) S. P. Belov, A. V. Burenin, O. L. Polyanski,
and S. M. Shapin,
1981, J. Mol. Spectrosc. 90, 579.
C. Puzzarini is thanked for providing the data from (2).
Transition frequencies with uncertainties larger than
0.15 MHz were not merged.
Transitions with ΔK = 0 and with
predicted uncertainties exceeding 5 MHz should be
viewed with caution; the same applies to transitions with
ΔK ≠ 0 and predicted
uncertainties larger than 0.5 MHz. In the case
of astronomical observations, the predictions should be
reliable throughout.
Even though 31P and H hyperfine structure
have been resolved in some of the laboratory experiments
such splitting is negligible for astronomical observations.
At low temperatures, it may be necessary to discern between
A-PH3 and E-PH3
The A state levels are described by
K = 3n, those of E state by
K = 3n ± 1. The nuclear
spin-weight ratio is 2 : 1 for A-PH3
with K > 0 and all other states,
respectively. Note:
The A1/A2 splitting may be resolvable
in astronomical observations.
The JK = 11 level
is the lowest E state level.
It is 8.3711 cm–1 above ground.
Note also that
the parity employed here differs from the
A1/A2 parity as well as
from the A+/A– parity.
A levels with + parity belong to A1
for even K and to A2 for odd K.
A levels with + parity belong to A+
for J + K even and to A–
for J + K odd. Additional confusion may
occur because the + sign has been omitted and transitions with
rounded A1/A2 splitting of
less than 0.1 kHz splitting have been merged. These
transitions look like they were between two A1
levels. Lower case characters designate – parity states
with K ≥ 10.
The dipole moment was determined in (5).
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