Knowledge Bank

The color center laser is continuously tunable between $2.3-3.3\mu m$ with single mode power between 1 - 15 mW. This relatively high power makes infrared. radiofrequency double resonance spectrocopy possible [1]. We have used this technique to study the $A1-A2$ splitting of $CH3F$ in the $\nu 4(J.K=1,1=1$ and $J,K=2,1=1$) state. This splitting can be represented by $\Delta \nu =(J+KY)!(J-KY)!\{q+qiJ(J+1)+qJJJ2(J+1)2.\}$ where the second and third terms are centrifugal distortion terms. We determined $q=16.04466(53)MHz.qJ=3.523(29)KHz$ and $qJJ=2.53(36)Hz$ for $K=1,l=1$ and $q=6.88835(72)KHz.qJ=4.6124(70)Hz$ and $qJJ=2.444(16)\times 10-3$ Us for $K=2.l=.1$ We also measured the electric dipole moment of $CH3F$ in the $\nu 4$ state using this technique. By applying a Stark field perpendicular to the Rf radiation, we could observe the splitting between M-components in the ground and $\nu 4$ states. Using the ratio of this splitting (when $J\prime \prime =K\prime \prime$ and $J\prime =K\prime )$ the dipole moment can be calculated according to $\mu \prime =\mu \prime \prime =\Delta \nu \prime (J\prime +1)\Delta \nu \prime \prime (J\prime \prime +1)$ which is independent of the Stark field. We determined $\mu \prime =1.8332(23)D$, which is calculated using the ground state dipole moment, $\mu \prime \prime =1.8585(5)D$, accurately determined by molecular beam electric resonance [2]. This study was conducted as a preliminary experiment for the planned IR-RF and IR-MW double resonance spectroscopy of molecular ions, which is in progress and will also be discussed.