Dispersed fluorescence spectroscopy of excited rovibrational states in S formaldehyde

Abstract

Dispersed fluorescence ͑DF͒ spectroscopy is used to explore the rovibrational structure of highly excited S 0 formaldehyde ͑H 2 CO͒. A narrowband laser excites formaldehyde molecules to a single S 1 rovibronic quantum state, and the resulting fluorescence is dispersed with a monochromator. DF spectra of ten vibrational levels with excitation in 2 , the carbon-oxygen stretch, and 4 , the out-of-plane bend, have been recorded, and the effective A, B, and C rotational constants are extracted. Five of the effective A rotational constants and seven of the effective B and C rotational constants are new to the literature. The dependence of these effective rotational constants on vibrational state are both calculated and discussed with regard to both the present and previous experiments. Particular attention is given to the manner in which that the effective A rotational constant depends on increasing excitation in 4 due to the strong A-axis 4 / 6 Coriolis interaction. For states where v 2 is less than two, quantitatively accurate values for the nonlinear dependence of the A rotational constant on quanta in 2 and 4 is achieved by a simultaneous consideration of the strong A-axis 4 / 6 Coriolis interaction and the 1 1 ↔4 2 , 1 1 ↔6 2 , and 5 1 ↔2 1 6 1 Fermi interactions.

K-Rotational Relaxation of S1 H2CO (v4 = 1, JKaKc = 101) via Dispersed Fluorescence Spectroscopy

“…The predicted spectrum includes spectroscopic branch notation, with the same horizontal scale for K a ′ ) 0, 2, 4, 6, 8 DF signals. Each stick in the predicted spectrum corresponds to a specific transition, and its height is proportional to the relative fluorescence intensity predicted by FORTRAN program ASYROT, 9 assuming A ) 8.070 cm -1 , B ) 1.2610 cm -1 , and C ) 1.1294 cm -1 for 2 1 4 2 H 2 CO. 10 Only the first five J-transitions are included in each branch. The experimental spectra include four DF spectra taken at 205, 500, 1000, and 2000 mTorr, with an 800 ns detection gate width and the DF intensity normalized to the central K a ′ ) 0 parent peak signal.…”

“…The predicted spectrum includes spectroscopic branch notation, with the same horizontal scale for K a ‘ = 0, 2, 4, 6, 8 DF signals. Each stick in the predicted spectrum corresponds to a specific transition, and its height is proportional to the relative fluorescence intensity predicted by FORTRAN program ASYROT, assuming A = 8.070 cm -1 , B = 1.2610 cm -1 , and C = 1.1294 cm -1 for 2 1 4 2 H 2 CO …”

Degenerate and two‐color resonant four‐wave mixing applied to the rotational characterization of high‐lying vibrational states of formaldehyde (Ã, 1A2)

“…39 In this case, the A rotational constant dependence is not accurately described by Eqn (3), and a more complex analysis is required. 40 In addition, the determined A constant of the 2 2 5 1 level might also include contributions from Coriolis-or Fermi-type resonances. A comparison of the calculated and observed intensity distributions in the DFWM spectrum for r R 1 region above 33 530 cm 1 provides a further indication for such perturbations (Fig.…”

Molecular spectroscopy and dynamics: a polyad-based perspective

“…Concerning 4-atom species, the premises for a global polyad vibrational Hamiltonian in NH 3 were established by Lehmann and also by Kleiner. 98,[238][239][240] Vibrational polyads were worked out by Polik for H 2 CO, 241,242 as well as for HFCO. 243 The vibrational energy pattern in other 4-atom molecules has been arranged into polyads, including for certain acetylene isotopologues (Section 3C), and for haloacetylenes by Mills.…”