Knowledge Bank

We have observed stimulated emission pumping (SEP) spectra of vibrationally excited $X~1\Sigma +$ HCP via its $C~1A\prime$ state. We measured high resolution SEP spectra of two thirds of the $22500cm-1-23200cm-1$ region. Since the $C~-X~$ transition is a parallel one, only $l\prime =0$ levels are accessible by allowed transitions. When the P(J) line is used an a pump transition, the R(J-2) and P(J) lines appear in the spectrum. We used P(2), P(4),\ldots . P(10) lines as pump transitions. There, 20 vibrational levels were found. Among them, 17 levels have definitely J = 0 level. This indicates that they are definitely $l\prime =0$ levels. In the previous SEP study via the $A~1A\prime \prime$ $stale1$, only pure bend overtone levels were observed in this region. It is expected that there is one Franck-Condon bright series (0, 38,0),(0, 36.1),(0, 34,2)\ldots (0,24, 7). Considering the level density, combination levels involving H atom radial motion must be excited. The B constants of these levels are in the range $0.63cm-1-0.76cm-1$. Compared with the B constant in the vibrational ground state, $0.666cm-1$, a B constant of more than $0.7cm-1$ is so large as to be of diagnostic significance. The 4 levels which have B constant of more than $0.72cm-1$ can be assigned as members of similar (n, v, 0),(ns v-2, 1)\ldots series built on $n\ne 0$ quanta of H---(CP) stretch. Detailed analysis will be presented.