# THE MAGNETIC ROTATION SPECTRUM OF FORMALDEHYDE: SINGLET-TRIPLET PERTURBATIONS IN THE $4^{1}$ and $4^{3}$ LEVELS OF THE $A^{1} A_{2}$ STATE OF $H_{2}CO$

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 Title: THE MAGNETIC ROTATION SPECTRUM OF FORMALDEHYDE: SINGLET-TRIPLET PERTURBATIONS IN THE $4^{1}$ and $4^{3}$ LEVELS OF THE $A^{1} A_{2}$ STATE OF $H_{2}CO$ Creators: Ramsay, D. A.; Till, S. M. Issue Date: 1979 Publisher: Ohio State University Abstract: Magnetic rotation spectra of the $4^{1}_{0}$ and $4^{3}_{0}$ bands of the $\tilde{A}^{1}A_{2} - \tilde{X}^{1}A_{1}$ system of formaldehyde have been photographed under high resolution . The $^{r}R$ and $^{p}P$ branches of these bands are found to be active and it is noted that the intensities appear to increase more rapidly with increasing $K_{a}$ in the MRS than in the absorption spectrum. The $4^{3}$ and $6^{1}$ levels are in Coriolis interaction at higher $K_{a}$ values, and some $^{r}R$ branches of the $6^{1}_{0}$ band are identified in the MRS. Several strong lines in the MRS are shown to be associated with $^{r}_{R}, ^{r}_{P}, ^{p}_{R}$ and $^{p}_{P}$ lines in the absorption spectrum and to reveal the presence of singlet- triplet perturbations. Only one perturbed rotational level is found in the $4^{1}_{0}$ band , but for the $4^{3}_{0}$ band several rotational levels are found to exhibit local perturbations, e.g., ${19}_{0}, 19, {19}_{1}, 19, {17}_{1}, 16, {10}_{2,8,} {10}_{2,9,} {11}_{2,9,} {17}_{3,14,} {17}_{3,15,} {18}_{3,15,}$ and ${18}_{3,16}$. These perturbations are produced by $\Delta J = \Delta N = \Delta K_{a} = 0$ interaction with the $4^{15}16^{1}$ level of the $a^{3}A_{2}$ state and by $\Delta J = \Delta N =0, \Delta K_{a} = \pm 1$ interactions with the $5^{1}6^{1}$ level. The matrix elements are of the order of $0.01 – 0.10cm^{-1}$. Description: Author Institution: URI: http://hdl.handle.net/1811/10900 Other Identifiers: 1979-RE-02