TO
MICROWAVE SPECTROSCOPY LABORATORY
Location:
Room No. 449 of the Salt
Research interest:
The ongoing research programmes in the Microwave Spectroscopy Laboratory
are based on the high resolution microwave/millimeterwave spectroscopic studies
of the gas phase rotational spectra of organic molecules leading to the
determination of their structures, conformations, barrier to internal rotation
and investigation of other properties, e.g. electric dipole moment, centrifugal
distortions and quadrupole hyperfine interactions etc.
Gas phase rotational spectra of molecules e.g., fluorinated phenols,
benzonitriles and a few allyl derivatives have been studied. Different
rotational isomers present in fluorinated phenols have been identified through
their characteristic rotational spectra and rotational parameters. 35Cl and 37Cl quadrupole hyperfine structures of
3-chlorobenzonitrile have been analyzed. Mono, di and tri fluoro- substituted
benzonitrile molecules have also been studied. In Allyl Isocyanate and
Isothiocyanates, the most predominant conformers in the gas phase have been
identified unambiguously through the analysis of their microwave spectrum.
Potential barriers hindering the internal rotation of the CH3 group have been determined
for different fluorine substituted Toluene and Tolunitrile compounds from the
internal rotation splitting of their rotational lines. 79Br and 81Br
quadrupole hyperfine structure analysis of 13CF3Br
has been completed.
New programmes:
1. Millimeterwave spectral studies of stable and transient molecules produced by DC glow discharge technique:
The construction of a millimeterwave spectrometer to study transient molecules of chemical and astrophysical interest has been completed. The spectrometer which, at present, works up to 120 GHz, is basically a source - modulated system combined with a free space cell of 1 meter length and 10 cm diameter. The cell is coupled with a DC discharge facility. Millimeterwave radiation is produced by using frequency multipliers, the fundamental radiation source being Klystrons and Gunn Diodes. Millimeterwave radiation is fed into the absorption cell by a waveguide horn and Teflon lens. A similar horn and lens arrangement is used to focus the mmwave power onto the detector after propagating through the cell. The klystron is frequency modulated by a double square wave of 50 kHz and the signal is detected by a phase sensitive detector in the 2f mode.
The
performance of the spectrometer has been tested by observing many absorption
signals of CS & FCN, in their ground and different excited vibrational states.
CS was generated inside the cell by a low pressure (20-30 mtorr) DC discharge (
1 kv, 50 mA ) of CS2
vapour. Strong 2nd and 4th harmonic signals were recorded which corresponds to
the J=1←0 and J=2←1 signals of CS at 48990.98 MHz and 97980.95 MHz
respectively.12C34S, 13C32S
signals were also successfully recorded. CS has been detected in the
interstellar space by radio astronomers. FCN was generated in a low pressure DC
discharge of different fluorobenzonitrile compounds. Three other cyanide
compounds e.g., ClCN, BrCN and ICN have also been generated by DC glow
discharge technique and their mmwave spectrum have been analyzed. Recently, the analysis of the mmwave rotational
spectra of DC discharge produced interstellar molecules e.g., Propyne, Propynal
and Propenal have been completed.
2. Measurement of broadband microwave
absorption and dielectric properties of low dimensional materials:
Studies on broadband microwave absorption and
dielectric properties of low dimensional materials e.g., conducting polymers,
nano composites and nano fibres etc. has been initiated. A new facility has
been set up for the measurement of dielectric constants, dielectric loss,
shielding effectiveness and different S-parameters e.g., S11, S12,
S21 and S22 of low dimensional materials in the frequency
range 10 MHz to 26 GHz. Measurements on
a few conducting polymers and nano materials are underway.
Future plan:
The future aim of this laboratory is to extend the frequency range of investigation and to improve upon the sensitivity and resolution of the newly constructed mmwave spectrometer in order to detect more weak signals belonging to molecular ions and radicals of astrophysical interest. For this purpose, digital averaging of the signals and phase locking of the millimeterwave sources has to be achieved. The present room temperature diode detector is to be replaced by InSb liquid helium cooled bolometer detector.
In the coming years, efforts will be made to
explore the domain of THz spectroscopy.
Facilities available:
(1) Conventional 100 kHz Stark modulated microwave spectrometer with RF-Microwave (MW) and MW-MW double resonance facility.
(2) Millimeterwave spectrometer to study the rotational spectra of DC discharge produced stable and transient molecules of chemical and astrophysical interest in the gas phase.
(3) A facility for the measurement of broadband microwave absorption and dielectric properties of low dimensional materials.
Selected publications:
(1).
Millimeterwave spectral studies of propynal (HCCCHO) produced by DC glow
discharge and ab initio DFT
calculation. A. I. Jaman, Rangana Bhattacharya, Debasish Mandal* and Abhijit K.
Das*. J. Atomic, Mol. & Optical Physics, Vol. 2011, Article ID 439019, 8
pages.
*
IACS, Kolkata
(2).Ionic Conductivity studies of Solid-State
PEG-PU based electrolytes for
energy applications. Naresh Chilaka*,
Shekar Bheemanapalli* K.Rajani Kumari* ,
A.I Jaman and Sutapa Ghosh*. (Communicated)
* IICT,
(3) Millimeterwave rotational spectra, barrier
to internal rotation and DFT calculations of o-tolunitrile. A. I. Jaman, P.
Hemant Kumar and P. R. Bangal. J. Atomic, Mol and Optical Physics, vol. 2011,
Article ID 480396, doi: 10.1155/2011/480396.
(4) Rotational spectrum of Propyne observed
in a DC glow discharge and ab initio DFT calculations. A. I. Jaman, P. Hemant
Kumar and P. R. Bangal. Asian J. of Spectroscopy (special issue, p 43-48,
2010).
(5) Millimeterwave spectrum and ab initio DFT
calculation of the C-gauche conformer of Allyl Isocyanate. A. I. Jaman and P.
R. Bangal. J. Mol. Spectrosc. 255, 134, 2009.
(6)Millimeter-wave spectrum of DC discharge
produced Cyanogen Iodide (ICN) in excited vibrational state. P. R. Varadwaj and
A. I. Jaman.
(7) Time-resolved Fourier transform emission
spectroscopy of laser ablation products. K.
(8) Millimeterwave spectrum of ICN, a transient molecule of chemical and astrophysical interest. A. I. Jaman. J. Phys.: Conference Series. 80, 012006, 2007.
(9) Microwave spectrum of trans 3-fluorophenol in excited torsional states. A. I. Jaman. J. Mol. Spectrosc. 245, 21, 2007.
(10) Millimeter-wave spectrum of 2, 3-difluorobenzonitrile and ab initio DFT calculations. P. R. Varadwaj and A. I. Jaman. J. Mol. Spectrosc. 239, 216, 2006.
(11) Assignment and analysis of the rotational spectrum of 3-chlorobenzonitrile. P. R. Varadwaj, A. I. Jaman, Z. Kisiel and L. Pszczolkowski. J. Mol. Spectrosc. 239, 88, 2006.
(12) Millimeter-wave spectroscopy of chloroacetylene (ClCCH) produced by electrical glow discharge. P. R. Varadwaj and A. I. Jaman. Procd. of Int.Conf.on Submm Sci.&Tech.Allied.Pub. p-97, 2006.
(13) Centrifugal distortion analysis of the millimeter-wave spectrum of 2-fluorobenzonitrile and ab initio DFT calculations. P. R. Varadwaj and A. I. Jaman. J. Mol.Spectrosc. 236, 70, 2006.
(14) Millimeter-wave spectrum of ClCN observed in a DC glow discharge and ab initio calculations. P. R. Varadwaj, P. R. Bangal and A. I. Jaman. J. Mol.Struct. 780-781, 17, 2006.
(15) An ab initio (RHF) and DFT-B3LYP level spectroscopic studies of BrCCCN and the analysis of atomic polar tensors. P. R. Varadwaj and P. R. Bangal. J. Mol. Struct.(Theochem). 730, 23, 2005.
(16) Hydrogen-bonding and protonation effects on the formation of charge transfer complex between para-benzoquinone and 2, 6-dimethoxy phenol. P. R. Bangal. Chem. Phys. Lett. 401, 200, 2005.
(17) Millimeter-wave spectrum of BrCN produced
by a
(18) Infrared-Radiofrequency double resonance
spectrometer: an unique machine to probe excited vibrational states. R. N.
Nandia, A. K. Bhattacharya and A. I. Jaman.
adeceased.
(19) Millimeter-wave spectroscopy of transient molecules produced in a DC discharge. A. I. Jaman. Pramana 61, 85, 2003.
(20) Microwave spectrum of 2,4-Difluorophenol: cis conformer. S. Chakrabarti and A. I. Jaman. J. Mol. Struct. 642, 93, 2002.
(21) Microwave spectrum and quadrupole
coupling constants of 13CF3Br.
(22) Microwave spectrum and quadrupole coupling constants of 2,3-difluorobenzonitrile. M. Onda, T. Kasagi and A. I. Jaman. J. Mol. Struct. 612, 167, 2002.
(23) Microwave spectrum and conformation in 2-Fluorophenylisothiocyanate. S. Chakrabarti and A. I. Jaman. J. Mol. Spectrosc. 202, 223, 2000.
(24) Centrifugal distortion analysis of the microwave spectrum of allyl isothiocyanate (C-gauche Conformer). A. I. Jaman. Pramana 53, 857, 1999.
(25) Microwave spectrum and barrier to internal rotation in Ortho-Tolunitrile. A. I. Jaman, S. Maiti and R. N. Nandi. J. Mol. Spectrosc. 192, 148, 1998.
(26) Microwave spectrum and barrier to internal rotation in 2,4-Difluorotoluene. S. Maiti, A. I. Jaman and R. N. Nandi. J. Mol. Spectrosc. 177, 29, 1996.
(27) Microwave spectrum of Allyl Isothiocyanate: Gauche comformer. S. Maiti, A. I. Jaman and R. N. Nandi. J. Mol. Spectrosc. 165, 168, 1994.
(28) Microwave spectrum of Allyl Isocyanate: Gauche conformer. S. Maiti, A. I. Jaman and R. N. Nandi. J. Mol. Spectrosc. 158, 8, 1993.
Work done in other laboratories:
(1) Time-resolved Fourier transform emission
spectroscopy of laser ablation products. K. Kawaguchi, N. Sanechika, Y.
Nishimura, R. Fujimori, T. N. Oka, Y. Hirahara, A. I. Jaman and S. Civis. Chem.
Phys. Lett. 463, 38, 2008.
(2) Submillimeterwave spectra of the AsH and AsD radicals in the X3sigma- electronic state. H. Fujiwara, K. Kobayashi, H. Ozeki, S. Saito and A. I. Jaman. J. Chem. Soc. Faraday Transaction 93(6), 1045, 1997.
(3) Rotational spectra, dipole moment and structure of SiF4--NH3 dimer. R. S. Rouff, T. Emilsson, A. I. Jaman, T. C. Germann and H. S. Gutowsky. J. Chem. Phys. 96, 3441, 1992.
(4) Rotational spectrum and structure of the linear HCN---HCCH dimer. A. I. Jaman, T. C. Germann, H. S. Gutowsky, J. D. Augspurger and C. E. Dykstra Chem. Phys. 154, 281, 1991.
Present Members:
E-mail: 
microwave.lab[at]saha.ac.in
This laboratory is currently looking for a young,
energetic and hard working graduate student who is willing to work in the
current and future programmes of this laboratory leading to his/her Ph.D
degree. Strong background in Physics/Physical Chemistry is essential. Must have
a UGC/CSIR fellowship.
Contact E-mail
address : aismail.jaman[at]saha.ac.in