4.12 Experimental Techniques
97
were used to detect molecular chirality, opening new perspectives for this technique.
For reviews on this subject, see Grabow (2013) and Pate et al. (2018).
4.12.3 Millimeterwave and Submillimeterwave
Spectroscopies
With the exception of some backward-wave oscillators which can operate up to 1 THz
(Winnewisser et al. 1994; Petkie et al. 1997), the conventional sources used in the
microwave range do not operate well at short wavelengths. One of the oldest methods
to obtain millimeterwaves and submillimeterwaves is the frequency multiplication
of a microwave source (King and Gordy 1953, 1954). In the early days, this method
required a lot of skill and was used by very few groups. Now, thanks to commercial
multipliers, this technique is much easier to use up to about 3 THz (Drouin et al.
2005; Pearson et al. 2011).
A more recent technique consists in producing a sideband source by photomixing
two lasers (Pine et al. 1996) or by mixing a far-infrared laser with a microwave source
(Verhoeve et al. 1990).
A third technique is to use a conventional Fourier transform infrared spectrometer. However, thermal sources give little power in the millimeter and submillimeter
region. This difficulty was recently solved by the use of a synchrotron radiation (SR)
as source. The application of SR to this field was pioneered in the mid-1990s by
Bengt Nelander at the MAX I storage ring in Lund, Sweden, and has become more
widespread since the opening of new dedicated facilities. A recent spectrometer is
described by Barros et al. (2015).
Finally, free-electron lasers such as FELIX (Oepts et al. 1995) can also be used
in the far-infrared range.
4.13 Software
• The analysis of rovibrational data has benefited from the introduction by Pickett
(1991) of a general code based on tensor algebra, allowing for flexible introduction
of custom Hamiltonian terms. The use of the SPFIT and SPCALC programs is
now standard. They calculate energies and intensities for asymmetric rotors and
linear molecules with up to 999 vibrational states and up to 9 spins. SPFIT is
used for fitting transitions and term values. SPCALC is used for predicting line
positions and strengths.
• JB95 from David F. Plusquellic is a graphical user interface program written in
the C programming language to aid in the analysis of complex molecular spectra.
Resources are provided for the deconvolution of multiple overlapping rotational
97
were used to detect molecular chirality, opening new perspectives for this technique.
For reviews on this subject, see Grabow (2013) and Pate et al. (2018).
4.12.3 Millimeterwave and Submillimeterwave
Spectroscopies
With the exception of some backward-wave oscillators which can operate up to 1 THz
(Winnewisser et al. 1994; Petkie et al. 1997), the conventional sources used in the
microwave range do not operate well at short wavelengths. One of the oldest methods
to obtain millimeterwaves and submillimeterwaves is the frequency multiplication
of a microwave source (King and Gordy 1953, 1954). In the early days, this method
required a lot of skill and was used by very few groups. Now, thanks to commercial
multipliers, this technique is much easier to use up to about 3 THz (Drouin et al.
2005; Pearson et al. 2011).
A more recent technique consists in producing a sideband source by photomixing
two lasers (Pine et al. 1996) or by mixing a far-infrared laser with a microwave source
(Verhoeve et al. 1990).
A third technique is to use a conventional Fourier transform infrared spectrometer. However, thermal sources give little power in the millimeter and submillimeter
region. This difficulty was recently solved by the use of a synchrotron radiation (SR)
as source. The application of SR to this field was pioneered in the mid-1990s by
Bengt Nelander at the MAX I storage ring in Lund, Sweden, and has become more
widespread since the opening of new dedicated facilities. A recent spectrometer is
described by Barros et al. (2015).
Finally, free-electron lasers such as FELIX (Oepts et al. 1995) can also be used
in the far-infrared range.
4.13 Software
• The analysis of rovibrational data has benefited from the introduction by Pickett
(1991) of a general code based on tensor algebra, allowing for flexible introduction
of custom Hamiltonian terms. The use of the SPFIT and SPCALC programs is
now standard. They calculate energies and intensities for asymmetric rotors and
linear molecules with up to 999 vibrational states and up to 9 spins. SPFIT is
used for fitting transitions and term values. SPCALC is used for predicting line
positions and strengths.
• JB95 from David F. Plusquellic is a graphical user interface program written in
the C programming language to aid in the analysis of complex molecular spectra.
Resources are provided for the deconvolution of multiple overlapping rotational