The observed rovibrational and rotational transition
frequencies have been described in
(1) H. S. P. Müller, P. Pracna, and V.M. Horneman,
2002, J. Mol. Spectrosc. 216, 397, in
(2) P. Pracna, H. S. P. Müller, S. Klee, and V.M. Horneman,
2004, Mol. Phys. 102, 1555,
and in references therein.
The ν_{9} band is the second lowest
and the strongest fundamental in propyne.
The ν_{9} band is a doubly degenerate vibration.
State number 1 describes k values ≤ 0,
while state number 2 indicates states with k > 0.
The data have been subjected to a combined fit consisting of
v_{10} = 0, 1, 2 and v_{9} = 1
pure rotational data as well as ν_{10}, ν_{9},
and 2ν_{10} – ν_{10}
rovibrational data.
A strong, isolated line has an estimated precision of
0.0002 cm^{–1}; the accuracies are probably
slightly worse because of calibration uncertainties.
The Coriolis interactions of v_{9} = 1 with
v_{10} = 1 and the Fermi interaction with
v_{10} = 2 described in (1) and (2),
have been taken into account. The latter occurs at K = 1
between l = –1 of v_{9} = 1 and
l = +2 of v_{10} = 2, causing
nonzero intensity in some transitions of 2ν_{10};
these transitions have the upper state number 3.
Its interactions with states of the next higher polyad
have not been taken into account in this prediction and the
Coriolis interaction with v_{10} = 2 at higher
K have not been considered in the current model. Therefore,
predictions for transitions with k ≤ –10
or k ≥ 13 should be viewed with caution.
The transition dipole moment has been derived from intensity
measurements of individual rovibrational transitions by
(3) G. Blanquet, J. Walrand, and M. DangNhu.
1992, Spectrochim. Acta, 48A, 1231.
Besides the ground vibrational state, the partition function takes
into account the states v_{10} = 1,
v_{9} = 1, and v_{10} = 2.
Their respective contributions are given in parentheses as long
as they are different from 0 within the quoted digits.
