98
T. Szidarovszky et al.
In summary, by changing the turn-on time of the dressing field, the initial wave
function can be manipulated, and in such a way the transition peaks observed in
the light-dressed spectrum can be influenced or controlled. However, this might
significantly complicate the interpretation of the spectrum.
4.5 Summary and Conclusions
We have presented a theoretical method to compute light-dressed spectra of molecules
dressed by medium-intensity laser fields (I = 10
7
− 5 × 10
9 Wcm
−2 in the numerical examples of this work). The approach is based on Floquet theory for deriving the
light-dressed states, which are expanded using field-free molecular eigenstates. Once
the light-dressed states are determined, the transition amplitudes induced between
them by a weak probe pulse are computed utilizing first-order perturbation theory.
A numerical example is given for the homonuclear diatomic molecule Na 2 , for
which the general formulae can be simplified and the rovibronic light-dressed spectra
can be interpreted straigthforwardly. The simulations indicate that the light dressing
process leads to the splitting of field-free peaks as well as the appearance of new
peaks, which correspond to transitions forbidden in the field-free case. Processes
corresponding to the well-known intensity borrowing and Autler–Townes effects of
molecular spectroscopy can also be observed.
Dependence of the light-dressed rovibronic spectrum of Na 2 on the dressing light
intensity and the dressing light wavelength was investigated, as well. It was found
that one can influence and control the peaks appearing in the light-dressed spectra
by manipulating the intensity and the wavelength of the dressing light.
We tested how the transition wavenumber of a forbidden field-free transition could
be determined by extrapolating light-dressed transition frequencies to the limit of
zero dressing-light intensity. The extrapolation scheme seemed to produce excellent
results.
Calculations assuming different initial temperatures of the molecular ensemble
prior to the dressing process reveal that the envelopes of the field-dressed spectra
are much less sensitive to the initial temperature than the individual spectral peaks,
similar to the field-free case.
Finally, it was shown that the initial wave function of the light-dressed system
can be modified significantly when the turn-on time of the dressing field is changed
from the adiabatic limit to shorter times, likely to result in significant changes in the
light-dressed spectrum, as well.
Acknowledgements This research was supported by the EU-funded Hungarian grant EFOP3.6.2-16-2017-00005. The authors are grateful to NKFIH for support (Grant No. PD124623 and
K119658).
T. Szidarovszky et al.
In summary, by changing the turn-on time of the dressing field, the initial wave
function can be manipulated, and in such a way the transition peaks observed in
the light-dressed spectrum can be influenced or controlled. However, this might
significantly complicate the interpretation of the spectrum.
4.5 Summary and Conclusions
We have presented a theoretical method to compute light-dressed spectra of molecules
dressed by medium-intensity laser fields (I = 10
7
− 5 × 10
9 Wcm
−2 in the numerical examples of this work). The approach is based on Floquet theory for deriving the
light-dressed states, which are expanded using field-free molecular eigenstates. Once
the light-dressed states are determined, the transition amplitudes induced between
them by a weak probe pulse are computed utilizing first-order perturbation theory.
A numerical example is given for the homonuclear diatomic molecule Na 2 , for
which the general formulae can be simplified and the rovibronic light-dressed spectra
can be interpreted straigthforwardly. The simulations indicate that the light dressing
process leads to the splitting of field-free peaks as well as the appearance of new
peaks, which correspond to transitions forbidden in the field-free case. Processes
corresponding to the well-known intensity borrowing and Autler–Townes effects of
molecular spectroscopy can also be observed.
Dependence of the light-dressed rovibronic spectrum of Na 2 on the dressing light
intensity and the dressing light wavelength was investigated, as well. It was found
that one can influence and control the peaks appearing in the light-dressed spectra
by manipulating the intensity and the wavelength of the dressing light.
We tested how the transition wavenumber of a forbidden field-free transition could
be determined by extrapolating light-dressed transition frequencies to the limit of
zero dressing-light intensity. The extrapolation scheme seemed to produce excellent
results.
Calculations assuming different initial temperatures of the molecular ensemble
prior to the dressing process reveal that the envelopes of the field-dressed spectra
are much less sensitive to the initial temperature than the individual spectral peaks,
similar to the field-free case.
Finally, it was shown that the initial wave function of the light-dressed system
can be modified significantly when the turn-on time of the dressing field is changed
from the adiabatic limit to shorter times, likely to result in significant changes in the
light-dressed spectrum, as well.
Acknowledgements This research was supported by the EU-funded Hungarian grant EFOP3.6.2-16-2017-00005. The authors are grateful to NKFIH for support (Grant No. PD124623 and
K119658).