Subhasis Panja - Academia.edu (original) (raw)
Papers by Subhasis Panja
Precise Time Synchronization and Clock Comparison through a White Rabbit Network based optical fi... more Precise Time Synchronization and Clock Comparison through a White Rabbit Network based optical fibre link all data recorded at CSIR-National Physical Laboratory , India
Metrology for Inclusive Growth of India, 2020
Time synchronization and frequency stability are crucial requirements in various cyber physical s... more Time synchronization and frequency stability are crucial requirements in various cyber physical systems (CPS) representing e-governance, navigation, smart technologies, financial and strategic sectors that finally create a self-sufficient and cyber secure digital India. To maintain these two parameters within the tolerance limit, they require a continuous traceability with respect to Coordinated Universal Time (UTC), which is realized at CSIR-NPL as IST described in Chapter 4 (Part 1). At present, time is not a legal entity in India. IST is used as official time but has not been legalized yet. In the absence of legal time and its implementation, cyber safety with time audit mechanism is not available to all sectors and CPS applications based on precise time synchronization. A detailed road map for time accuracy and traceability requirements of various sectors has been discussed with an emphasis on cyber security and cyber physical systems in India. The steps needed have been listed to synchronize all clocks in the country to IST, starting from legalization and consequent implementation of IST in India. A new policy has been proposed for time accreditation, and audit mechanism by elaborating on usage of existing and new
Chemical Physics Letters, Jan 24, 2003
Spectrochim Acta Pt a Mol Bio, 2004
This paper mainly dwells on photophysics of 4-(imidazole-1-yl) phenol (IDP) in different solvents... more This paper mainly dwells on photophysics of 4-(imidazole-1-yl) phenol (IDP) in different solvents and temperatures from the investigations of absorption, emission and laser flash photolysis and also on the nature of complexation with beta-cyclodextrin (CD) in ground and excited states. IDP makes 1:1 inclusion complex with beta-CD in ground, excited singlet and also in triplet states. The orientation of complex could be ascertained as imidazole moiety stays inside the cavity with phenol moiety stays in the bulk. A proposed energy level scheme unveils that vibronic interaction and spin-orbit interaction are found to be active differently in aprotic and protic solvents.
Chemical Physics Letters, Jul 1, 2007
... Ruth M. Burke a , William E. Boxford a , Subhasis Panja b , Steen Brøndsted Nielsen b and Car... more ... Ruth M. Burke a , William E. Boxford a , Subhasis Panja b , Steen Brøndsted Nielsen b and Caroline EH Dessent a , Corresponding Author Contact Information , E-mail The Corresponding Author. a Department of Chemistry, University of York, Heslington, York YO10 4DF, UK. ...
International Journal of Mass Spectrometry, Oct 1, 2008
Complexes of doubly protonated 1, n-diaminoalkanes with one or two molecules of 18-crown-6-ether ... more Complexes of doubly protonated 1, n-diaminoalkanes with one or two molecules of 18-crown-6-ether undergo consecutive and competitive dissociations upon electron capture from a free thermal electron and femtosecond collisional electron transfer from Na and Cs ...
The Journal of Chemical Physics, Nov 14, 2008
The behavior of protonated tryptophan (TrpH(+)) and its complex with 18-crown-6-ether (CE) after ... more The behavior of protonated tryptophan (TrpH(+)) and its complex with 18-crown-6-ether (CE) after photoexcitation has been explored based on measurements of dissociation lifetimes, fragmentation channels, and absorption spectra using an electrostatic ion storage ring. A recent implementation of pulsed power supplies for the ring elements with microsecond response times allows us to identify the daughter ion fragment masses and to disentangle fragmentation that occurs from excited states immediately after photoexcitation from that occurring on a longer time scale of several microseconds to milliseconds. We find that attachment of crown ether significantly alters the dissociation channels since it renders the pisigma(*)(NH(3)) state inaccessible and hence prevents the N-H bond breakage which is an important fragmentation channel of TrpH(+). As a result, on a long time scale (>10 micros), photoexcited TrpH(+)(CE) decays exponentially whereas TrpH(+) displays a power-law decay. The only ions remaining in the latter case are Trp(+) radical cations with a broad internal energy distribution caused by the departing hydrogen. Large changes in the fragment branching ratios as functions of excitation wavelength between 210 and 290 nm were found for both TrpH(+) and TrpH(+)(CE).
New Journal of Physics, 2006
By focusing 805 nm pulses of low energy (0.2-1 mJ) into atmospheric-pressure argon, a supercontin... more By focusing 805 nm pulses of low energy (0.2-1 mJ) into atmospheric-pressure argon, a supercontinuum is generated with a shortwavelength cutoff of 640, 250 and 210 nm for initial pulse durations of 45, 10 and 6 fs, respectively. It is shown numerically that the large shift of the UV cutoff and many features of the spectrum are caused by terms beyond the slowly-varyingenvelope approximation (SVEA). Their effect on pulse compression and filament length is also discussed.
Chem Phys Lett, 2001
... Referred to by: Dynamics of twisted intramolecular charge transfer process of 4-N, N-dimethy... more ... Referred to by: Dynamics of twisted intramolecular charge transfer process of 4-N, N-dimethylaminocinnamic ... 3). With addition of more α-CD another cyclodextrin cone can accommodate the rest portion of ... NMe 2 group) of DACA faces some restriction on its free rotation ...
Review of Scientific Instruments, 2015
Physical Chemistry Chemical Physics, 2009
(H(+))(H(2)O)(n) ions (n = 1-72) at 50 keV energies were brought to collide with caesium atoms. T... more (H(+))(H(2)O)(n) ions (n = 1-72) at 50 keV energies were brought to collide with caesium atoms. The analysis of the products formed for clusters having n > 4 shows that this leads to the formation of a population of (OH(-))(H(2)O)(m) ions with a variable number m. On average, more than half of the water molecules are lost from the cluster in the process. A model can explain the experimental observations where two successive collisions occur within a time period of less than 100 ns. One-electron transfer from caesium to water leading to the loss of one hydrogen atom occurs at each stage. While the first stage is by itself exothermic, the second stage requires additional energy from collisional energy transfer.
The Journal of Physical Chemistry A, 2003
... Papia Chowdhury, Subhasis Panja, and Sankar Chakravorti*. Department of Spectroscopy, Indian ... more ... Papia Chowdhury, Subhasis Panja, and Sankar Chakravorti*. Department of Spectroscopy, Indian Association for the Cultivation of Science, Jadavpur, Kolkata 700032, India. J. Phys. Chem. A , 2003, 107 (1), pp 8390. DOI: 10.1021 ...
The Journal of Physical Chemistry A, 2007
Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, 2004
This paper mainly dwells on photophysics of 4-(imidazole-1-yl) phenol (IDP) in different solvents... more This paper mainly dwells on photophysics of 4-(imidazole-1-yl) phenol (IDP) in different solvents and temperatures from the investigations of absorption, emission and laser flash photolysis and also on the nature of complexation with beta-cyclodextrin (CD) in ground and excited states. IDP makes 1:1 inclusion complex with beta-CD in ground, excited singlet and also in triplet states. The orientation of complex could be ascertained as imidazole moiety stays inside the cavity with phenol moiety stays in the bulk. A proposed energy level scheme unveils that vibronic interaction and spin-orbit interaction are found to be active differently in aprotic and protic solvents.
Review of Scientific Instruments, 2008
A new method for time-resolved daughter ion mass spectrometry is presented, based on the electros... more A new method for time-resolved daughter ion mass spectrometry is presented, based on the electrostatic ion storage ring in Aarhus, ELISA. Ions with high internal energy, e.g., as a result of photoexcitation, dissociate and the yield of neutrals is monitored as a function of time. This gives information on lifetimes in the microsecond to millisecond time range but no information on the fragment masses. To determine the dissociation channels, we have introduced pulsed supplies with switching times of a few microseconds. This allows rapid switching from storage of parent ions to storage of daughter ions, which are dumped into a detector after a number of revolutions in the ring. A fragment mass spectrum is obtained by monitoring the daughter ion signal as a function of the ring voltages. This technique allows identification of the dissociation channels and determination of the time dependent competition between these channels.
Molecular Physics, 2006
ABSTRACT Photochemically, s-cis-dienes can undergo cis-trans isomerization or electrocyclic ring ... more ABSTRACT Photochemically, s-cis-dienes can undergo cis-trans isomerization or electrocyclic ring closure to cyclobutenes. Modern quantum chemistry predicts that both reactions can originate from the same conical intersection and explains thereby why photochemical ring opening of cyclobutenes to dienes is often not stereospecific, although ring closure of dienes is. Evidence is found that the reaction path already branches earlier, investigating two cyclic dienes which were excited by a femtosecond UV pulse in the gas phase and probed by photoionization at 810 nm. The multistep path is assigned to the excited-state surfaces and ring closure of the ground-state trans isomers is also detected.
Precise Time Synchronization and Clock Comparison through a White Rabbit Network based optical fi... more Precise Time Synchronization and Clock Comparison through a White Rabbit Network based optical fibre link all data recorded at CSIR-National Physical Laboratory , India
Metrology for Inclusive Growth of India, 2020
Time synchronization and frequency stability are crucial requirements in various cyber physical s... more Time synchronization and frequency stability are crucial requirements in various cyber physical systems (CPS) representing e-governance, navigation, smart technologies, financial and strategic sectors that finally create a self-sufficient and cyber secure digital India. To maintain these two parameters within the tolerance limit, they require a continuous traceability with respect to Coordinated Universal Time (UTC), which is realized at CSIR-NPL as IST described in Chapter 4 (Part 1). At present, time is not a legal entity in India. IST is used as official time but has not been legalized yet. In the absence of legal time and its implementation, cyber safety with time audit mechanism is not available to all sectors and CPS applications based on precise time synchronization. A detailed road map for time accuracy and traceability requirements of various sectors has been discussed with an emphasis on cyber security and cyber physical systems in India. The steps needed have been listed to synchronize all clocks in the country to IST, starting from legalization and consequent implementation of IST in India. A new policy has been proposed for time accreditation, and audit mechanism by elaborating on usage of existing and new
Chemical Physics Letters, Jan 24, 2003
Spectrochim Acta Pt a Mol Bio, 2004
This paper mainly dwells on photophysics of 4-(imidazole-1-yl) phenol (IDP) in different solvents... more This paper mainly dwells on photophysics of 4-(imidazole-1-yl) phenol (IDP) in different solvents and temperatures from the investigations of absorption, emission and laser flash photolysis and also on the nature of complexation with beta-cyclodextrin (CD) in ground and excited states. IDP makes 1:1 inclusion complex with beta-CD in ground, excited singlet and also in triplet states. The orientation of complex could be ascertained as imidazole moiety stays inside the cavity with phenol moiety stays in the bulk. A proposed energy level scheme unveils that vibronic interaction and spin-orbit interaction are found to be active differently in aprotic and protic solvents.
Chemical Physics Letters, Jul 1, 2007
... Ruth M. Burke a , William E. Boxford a , Subhasis Panja b , Steen Brøndsted Nielsen b and Car... more ... Ruth M. Burke a , William E. Boxford a , Subhasis Panja b , Steen Brøndsted Nielsen b and Caroline EH Dessent a , Corresponding Author Contact Information , E-mail The Corresponding Author. a Department of Chemistry, University of York, Heslington, York YO10 4DF, UK. ...
International Journal of Mass Spectrometry, Oct 1, 2008
Complexes of doubly protonated 1, n-diaminoalkanes with one or two molecules of 18-crown-6-ether ... more Complexes of doubly protonated 1, n-diaminoalkanes with one or two molecules of 18-crown-6-ether undergo consecutive and competitive dissociations upon electron capture from a free thermal electron and femtosecond collisional electron transfer from Na and Cs ...
The Journal of Chemical Physics, Nov 14, 2008
The behavior of protonated tryptophan (TrpH(+)) and its complex with 18-crown-6-ether (CE) after ... more The behavior of protonated tryptophan (TrpH(+)) and its complex with 18-crown-6-ether (CE) after photoexcitation has been explored based on measurements of dissociation lifetimes, fragmentation channels, and absorption spectra using an electrostatic ion storage ring. A recent implementation of pulsed power supplies for the ring elements with microsecond response times allows us to identify the daughter ion fragment masses and to disentangle fragmentation that occurs from excited states immediately after photoexcitation from that occurring on a longer time scale of several microseconds to milliseconds. We find that attachment of crown ether significantly alters the dissociation channels since it renders the pisigma(*)(NH(3)) state inaccessible and hence prevents the N-H bond breakage which is an important fragmentation channel of TrpH(+). As a result, on a long time scale (>10 micros), photoexcited TrpH(+)(CE) decays exponentially whereas TrpH(+) displays a power-law decay. The only ions remaining in the latter case are Trp(+) radical cations with a broad internal energy distribution caused by the departing hydrogen. Large changes in the fragment branching ratios as functions of excitation wavelength between 210 and 290 nm were found for both TrpH(+) and TrpH(+)(CE).
New Journal of Physics, 2006
By focusing 805 nm pulses of low energy (0.2-1 mJ) into atmospheric-pressure argon, a supercontin... more By focusing 805 nm pulses of low energy (0.2-1 mJ) into atmospheric-pressure argon, a supercontinuum is generated with a shortwavelength cutoff of 640, 250 and 210 nm for initial pulse durations of 45, 10 and 6 fs, respectively. It is shown numerically that the large shift of the UV cutoff and many features of the spectrum are caused by terms beyond the slowly-varyingenvelope approximation (SVEA). Their effect on pulse compression and filament length is also discussed.
Chem Phys Lett, 2001
... Referred to by: Dynamics of twisted intramolecular charge transfer process of 4-N, N-dimethy... more ... Referred to by: Dynamics of twisted intramolecular charge transfer process of 4-N, N-dimethylaminocinnamic ... 3). With addition of more α-CD another cyclodextrin cone can accommodate the rest portion of ... NMe 2 group) of DACA faces some restriction on its free rotation ...
Review of Scientific Instruments, 2015
Physical Chemistry Chemical Physics, 2009
(H(+))(H(2)O)(n) ions (n = 1-72) at 50 keV energies were brought to collide with caesium atoms. T... more (H(+))(H(2)O)(n) ions (n = 1-72) at 50 keV energies were brought to collide with caesium atoms. The analysis of the products formed for clusters having n > 4 shows that this leads to the formation of a population of (OH(-))(H(2)O)(m) ions with a variable number m. On average, more than half of the water molecules are lost from the cluster in the process. A model can explain the experimental observations where two successive collisions occur within a time period of less than 100 ns. One-electron transfer from caesium to water leading to the loss of one hydrogen atom occurs at each stage. While the first stage is by itself exothermic, the second stage requires additional energy from collisional energy transfer.
The Journal of Physical Chemistry A, 2003
... Papia Chowdhury, Subhasis Panja, and Sankar Chakravorti*. Department of Spectroscopy, Indian ... more ... Papia Chowdhury, Subhasis Panja, and Sankar Chakravorti*. Department of Spectroscopy, Indian Association for the Cultivation of Science, Jadavpur, Kolkata 700032, India. J. Phys. Chem. A , 2003, 107 (1), pp 8390. DOI: 10.1021 ...
The Journal of Physical Chemistry A, 2007
Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, 2004
This paper mainly dwells on photophysics of 4-(imidazole-1-yl) phenol (IDP) in different solvents... more This paper mainly dwells on photophysics of 4-(imidazole-1-yl) phenol (IDP) in different solvents and temperatures from the investigations of absorption, emission and laser flash photolysis and also on the nature of complexation with beta-cyclodextrin (CD) in ground and excited states. IDP makes 1:1 inclusion complex with beta-CD in ground, excited singlet and also in triplet states. The orientation of complex could be ascertained as imidazole moiety stays inside the cavity with phenol moiety stays in the bulk. A proposed energy level scheme unveils that vibronic interaction and spin-orbit interaction are found to be active differently in aprotic and protic solvents.
Review of Scientific Instruments, 2008
A new method for time-resolved daughter ion mass spectrometry is presented, based on the electros... more A new method for time-resolved daughter ion mass spectrometry is presented, based on the electrostatic ion storage ring in Aarhus, ELISA. Ions with high internal energy, e.g., as a result of photoexcitation, dissociate and the yield of neutrals is monitored as a function of time. This gives information on lifetimes in the microsecond to millisecond time range but no information on the fragment masses. To determine the dissociation channels, we have introduced pulsed supplies with switching times of a few microseconds. This allows rapid switching from storage of parent ions to storage of daughter ions, which are dumped into a detector after a number of revolutions in the ring. A fragment mass spectrum is obtained by monitoring the daughter ion signal as a function of the ring voltages. This technique allows identification of the dissociation channels and determination of the time dependent competition between these channels.
Molecular Physics, 2006
ABSTRACT Photochemically, s-cis-dienes can undergo cis-trans isomerization or electrocyclic ring ... more ABSTRACT Photochemically, s-cis-dienes can undergo cis-trans isomerization or electrocyclic ring closure to cyclobutenes. Modern quantum chemistry predicts that both reactions can originate from the same conical intersection and explains thereby why photochemical ring opening of cyclobutenes to dienes is often not stereospecific, although ring closure of dienes is. Evidence is found that the reaction path already branches earlier, investigating two cyclic dienes which were excited by a femtosecond UV pulse in the gas phase and probed by photoionization at 810 nm. The multistep path is assigned to the excited-state surfaces and ring closure of the ground-state trans isomers is also detected.