MicroWave Spectroscopy Laboratory
















Main directions of activity Studies of the molecular spectra Accurate bond dissociation energy

Fig. 1. Survey photofragment spectrum of HD16O from the gateway state, prepared by double resonance transition (normal mode vibrational notations) [27984.79 cm-1 (0,0,9), 101 ]→[(0,0,4), 000 ]→[(0,0,0), 101] to the states with quantum numbers J =1, 2. The spectrum is measured at the total water vapor pressure of 100 μbar (50 μbar partial pressure of HDO) by detecting the ground state OD and plotted in function of the total HD16O rovibrational energy. Schematic energy level diagram and excitation scheme employed in experiments is presented in figure 1 here.

 

Fig. 2. Sample photofragment spectra of HD16O transitions from the gateway states, prepared by double resonance transition (normal mode vibrational notations):

( a ) [27984.79 cm-1 (0,0,9), 101] → [(0,0,4), 000] → [(0,0,0), 101],

( b ) [28013.13 cm-1 (0,0,9), 202] → [(0,0,4), 101] → [(0,0,0) 202],

( c ) [25376.1 cm-1 (0,0,8), 202] → [(0,0,4), 101] → [(0,0,0) 202],

( d ) [25376.1 cm-1 (0,0,8), 000]→ [(0,0,4), 101] → [(0,0,0) 000];

and fits of the continuum onsets (red lines) by the Wigner threshold law with J= 2, 3, 3, 1 for (a)(d) respectively.

The spectra are measured by detecting the ground state OD fragments and labeled by the accessible angular momentum quantum numbers. Large peaks of the traces (b) and (c) go beyond the vertical scale. In (a)(c) the fits ignore the large absorption peaks below the onset for an appropriate fit of the baseline.

 

Table 1. Measured and calculated bond dissociation energies for different water isotopologues.

Bond

Bond dissociation energy ( cm -1 )

 

ab initio

Experiment

Difference

16 OH-H

41146.0

41 145.92( 0 .12)

0 .08

18 OH-H

41154.2

41154.4(0.2)

-0.2

16 OD-H

41239.7

41239.7(0.2)

0

For more detailes see Ref.3 (2013) .

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