Knowledge Bank

Collisional energy transfer in samples containing 2 m Torr of $\mathrm{<mrow\; data-mjx-texclass="ORD">12</mrow>}CH3F$ or $\mathrm{<mrow\; data-mjx-texclass="ORD">13</mrow>}CH3F$ in much higher concentrations of foreign gases such as $\mathrm{<mrow\; data-mjx-texclass="ORD">13</mrow>}CH3F$ or $\mathrm{<mrow\; data-mjx-texclass="ORD">12</mrow>}CH3F$, $H2$, He, Ar, or Xe have been studied by the method of four-level infrared-infrared double resonance. In each case a transition in the $\nu 3$ fundamental and was pumped by a $CO2$ laser coincidence and the lineshapes of a variety of transitions in the $\nu 3$ fundamental band and the $2\nu 3\leftarrow \nu 3$ hot band were recorded by scanning an infrared microwave sideband laser of the Magerl design$.1$ With methyl fluoride, $H2$, or He as the foreign gas at relatively low pressure (50 mTorr), the lineshapes of the probed transitions consist of a narrow spike plus a Gaussian for pump-probe combinations for which $\Delta k=3n$ ($n=0$ or an integer) and only a Gaussian for $\Delta k\ne 3n$, as has been observed in pure $\mathrm{<mrow\; data-mjx-texclass="ORD">13</mrow>}CH3F2$ and $\mathrm{<mrow\; data-mjx-texclass="ORD">12</mrow>}CH3F3$. With Ar and especially Xe the lineshapes are almost entirely Gaussian, although the $\Delta k=3n$ transitions are more intense than the $\Delta k\ne 3n$ transitions. With high pressures (1 - 12 Torr) of Ar, the width of the double resonance lineshape is substantially larger than the single resonance lineshape for the same sample and the center frequency of the double resonance undergoes a shift, proportional to pressure, to frequencies corresponding to velocity groups with the opposite sign of the velocity component pumped. The shift in frequency for the double resonance is substantially greater than the shift for the single resonance in the same sample. Collisional energy transfer from $v3=1$ to $v6=1$ in $\mathrm{<mrow\; data-mjx-texclass="ORD">12</mrow>}CH3F$ has also been observed in these systems by pumping a transition in the $\nu 3$ band and probing a transition in the $\nu 3+\nu 6\leftarrow \nu 6$ band; no transferred spikes have been seen for this vibrational energy transfer. Collisional energy transfer from $v3=1$ in $\mathrm{<mrow\; data-mjx-texclass="ORD">13</mrow>}CH3F$ to $v3=1$ and $v6=1$ in $\mathrm{<mrow\; data-mjx-texclass="ORD">12</mrow>}CH3F$ has also been observed.