Search results for: Hari P. Upadhyaya

Items from 1 to 20 out of 46 results

article

Theoretical Study on the Dissociation Mechanism of Thiophene in the UV Photoabsorption, Ionization, and Electron Attachment Processes

Hari P. Upadhyaya

International Journal of Quantum Chemistry > 124 > 20 > n/a - n/a

A computational study on the intricate mechanism of thiophene ring‐fragmentation (TRF) in the UV photodissociation, dissociative ionization, and dissociative electron attachment process has been performed. The complete fragmentation process is studied using high level G4 composite method for neutral, cationic, and anionic species by elucidating a detailed mechanism for various reaction channels. The...

article

Theoretical studies on the kinetics and mechanism of hydroxyl radical reaction with quinclorac and quinmerac herbicides in aqueous media

Hari P. Upadhyaya

International Journal of Quantum Chemistry > 124 > 11 > n/a - n/a

The kinetic and mechanistic studies for the reaction of hydroxyl radical with two quinoline based herbicides, namely, quinclorac and quinmerac has been performed using various computational methods in aqueous media. Geometry optimizations were performed using Density Functional Theory (DFT) methods including water as the solvent. Local reactivity parameters of these herbicides towards the ^•OH radical...

article

Ground‐state dissociation pathways for the molecular cation of 2‐chlorothiophene: A time‐of‐flight mass spectrometry and computational study

Hari P. Upadhyaya

Rapid Communications in Mass Spectrometry > 33 > 20 > 1598 - 1612

Rationale Halogenated thiophenes are an important class of compounds mostly used in the synthesis of various materials, showing unusual electronic and optical properties. The Thiophene Ring Fragmentation (TRF) process is widely used in synthetic chemistry. In this study, the fragmentation pattern of the molecular cation of halogenated thiophene, namely, 2‐chlorothiophene, was monitored to establish...

article

Rate coefficients of hydroxyl radical reaction with dimethyl ether over a temperature range of 257–333 K

Monali Kawade, Asmita Sharma, D. Srinivas, Ankur Saha, more

Chemical Physics Letters > 2018 > 706 > C > 558-563

The reaction of dimethyl ether (DME) with OH radical was studied using a laser photolysis-laser induced fluorescence technique in the temperature range of 257–333 K at 30 Torr. The temperature dependent rate coefficient is represented by the expression, kT=9.7±1.0×10-12exp-380±25/Tcm3molecules-1s-1 and atmospheric lifetime was found to be 4.7 days. To elucidate the reaction mechanism and complement...

article

Kinetics of gas phase OH radical reaction with thiophene in the 272–353K temperature range: A laser induced fluorescence study

Monali N. Kawade, D. Srinivas, Hari P. Upadhyaya

Chemical Physics Letters > 2017 > 682 > C > 154-159

Absolute rate coefficient for the gas phase reaction of OH radical with thiophene has been measured using the laser photolysis (LP) – laser induced fluorescence (LIF) technique. The kinetics measurements were done over the temperature range of 272–353K and pressure range of 20–30Torr. The bimolecular rate coefficients obtained were pressure independent in the above pressure range and showed Arrhenius...

article

Resonance enhanced multiphoton ionization − time of flight (REMPI-TOF) detection of Br (2Pj) atoms in the photodissociation of 4-bromo-2,3,5,6-tetrafluoropyridine at 234nm: Effect of low-lying πσ* states

D. Srinivas, Y. Sajeev, Hari P. Upadhyaya

Journal of Photochemistry and Photobiology A: Chemistry > 2017 > 345 > C > 1-10

The photodissociation dynamics of 4-bromo-2,3,5,6-tetrafluoropyridine (BTFP) have been studied in a supersonic molecular beam around 234nm, which prepares the molecule in its ππ* state. The dynamics of the CBr bond dissociation have been investigated using resonance-enhanced multiphoton ionization coupled with time-of-flight mass spectrometer (REMPI-TOFMS) by detecting the nascent spin orbit states...

article

Dissociation pathways for the molecular cation of 3,4‐dichloro‐1,2,5‐thiadiazole: A time‐of‐flight mass spectrometry and computational study

D. Srinivas, Hari P. Upadhyaya

Rapid Communications in Mass Spectrometry > 31 > 1 > 121 - 128

Rationale 1,2,5‐Thiadiazoles are an important class of compounds mostly used in synthetic chemistry, and as herbicides, insecticides, drugs, organic conductors, etc. Recently, they have been used as a source for the generation and study of nitrile N‐sulfides, RCNS, and its isomers. In this study, we monitor the fragmentation pattern of ionic halogenated 1,2,5‐thiadiazoles, namely, 3,4‐dichloro‐1,2,5‐thiadiazole,...

article

Ground state dissociation pathways for 3,4,-dichloro-1,2,5-thiadiazole: Spectroscopic observation and fate of NCC(Cl2)NS isomer

D. Srinivas, Hari P. Upadhyaya

Chemical Physics Letters > 2016 > 660 > C > 182-188

Photodissociation pathways for 3,4-dichloro-1,2,5-thiadiazole was investigated in its ground state at various wavelengths in the UV region. The photolysis products were identified by the UV absorption and emission spectroscopy. Molecular chlorine (Cl₂) elimination was observed using absorption methods in the UV region. UV absorption and quantum calculation confirms the migration of chlorine atom and...

article

Chlorine atom formation dynamics in the dissociation of halogenated pyridines after photoexcitation at 235nm: A resonance enhanced multiphoton ionization-time of flight (REMPI-TOF) study

D. Srinivas, Hari P. Upadhyaya

Chemical Physics > 2016 > 472 > C > 208-217

The photodissociation dynamics of halogen substituted pyridines, namely, 3-chloropyridine (ClPy) and 3-chloro-2,4,5,6-tetrafluoropyridine (ClFPy), has been studied around 235nm by detecting chlorine atoms in their spin orbit states Cl(²P_3/2) and Cl^∗(²P_1/2) using the REMPI-TOF technique. We have determined the translational energy distribution, the recoil anisotropy parameter, β, and the spin–orbit...

article

Dynamics of Cl(2Pj) formation in the photodissociation of halogenated thiadiazole at 235nm: A resonance enhanced multiphoton ionization-time of flight (REMPI-TOF) study

D. Srinivas, Hari P. Upadhyaya

Journal of Photochemistry and Photobiology A: Chemistry > 2016 > 322-323 > C > 41-52

In one colour experiment, the photodissociation dynamics of halogen substituted thiadiazole, namely, 3,4-dichloro-1,2,5-thiadiazole, has been studied in a supersonic molecular beam around 235nm, which prepares the molecules in its π–π* state. The study is conducted using resonance enhanced multiphoton ionization (REMPI) time-of-flight (TOF) technique, by detecting the nascent state of the primary...

article

Dynamics of OH formation in the photodissociation of enolic-acetonylacetone at 193nm

Hari P. Upadhyaya

Journal of Photochemistry and Photobiology A: Chemistry > 2016 > 318 > C > 56-63

The photodissociation dynamics of enolic-acetonylacetone (H₃CC(O)CH₂CH C(OH)CH₃), in gas phase, is studied using Laser Photolysis–Laser Induced Fluorescence (LP–LIF) technique at room temperature. The nascent state distribution of the OH radical is probed formed after photo-excitation of the parent molecule to its πC=C−πC=C* state using 193nm laser light. The ro-vibrational distribution of the nascent...

article

Photodissociation dynamics of 2-chloro-6-nitrotoluene and nitrocyclopentane in gas phase: Laser-induced fluorescence detection of OH

Monali N. Kawade, Ankur Saha, Hari P. Upadhyaya, Awadhesh Kumar, more

Chemical Physics > 2014 > 443 > Complete > 123-132

Photodissociation of 2-chloro-6-nitrotoluene (ClNT) at 193, 248 and 266nm and nitrocyclopentane (NCP) at 193nm leads to the formation of OH, as detected by laser-induced fluorescence (LIF). The nascent OH produced from the photolysis of ClNT at all the wavelengths is vibrationally cold, with the Boltzmann type rotational state distributions. However, the nascent OH product from NCP is in the ground...

article

OH formation dynamics in 193nm photolysis of 2-methoxyethanol: A laser induced fluorescence study

Sumana SenGupta, Hari P. Upadhyaya, Awadhesh Kumar, Prakash D. Naik

Chemical Physics > 2014 > 443 > Complete > 8-16

Dynamics of OH radical formation in the 193nm photolysis of 2-methoxyethanol is studied using Laser Photolysis–Laser Induced Fluorescence technique. The nascent state distribution of the OH radical is measured. The OH fragments are formed vibrationally cold, characterized by a Boltzmann-like single rotational temperature of 450±100K. The spin–orbit and Λ-doublet ratios of OH fragments are measured...

article

Resonance enhanced multiphoton ionization time-of-flight (REMPI-TOF) study of tetrachloroethylene photodissociation at 235nm: Role of bound π-σC-Cl∗ state

Ankur Saha, Hari P. Upadhyaya, Awadhesh Kumar, Prakash D. Naik

Chemical Physics > 2014 > 428 > Complete > 127-136

In one-color REMPI-TOF experiment, the photodissociation dynamics of tetrachloroethylene has been studied by probing the chlorine atom photofragments, namely, Cl ( ² P _3/2 ) and Cl ^∗ ( ² P _1/2 ), using 2+1 REMPI scheme in the 234–236nm region. We have determined the centre-of-mass photofragment speed distribution, recoil anisotropy parameter (β), and the spin–orbit...

article

Photoexcitation of 2-bromo-2-chloro-1,1,1-trifluoroethane (halothane) to repulsive surface nσ∗(C–Br) at 234 nm: Dynamics of C–Br and C–Cl bond rupture

Ankur Saha, Monali N. Kawade, Hari P. Upadhyaya, Awadhesh Kumar, more

Chemical Physics > 2013 > 416 > Complete > 1-10

The photodissociation dynamics of 2-bromo-2-chloro-1,1,1-trifluoroethane (halothane) have been studied near 234nm, in a molecular beam environment, employing resonance-enhanced multiphoton ionization with time-of-flight mass spectrometer (REMPI-TOF-MS). Both bromine and chlorine atoms are detected in both the ground and spin–orbit excited states. The C–Br bond scission is observed predominantly due...

article

Resonance enhanced multiphoton ionization time-of-flight (REMPI-TOF) study of phosphorous oxychloride (POCl3) dissociation at 235nm: Dynamics of Cl(2Pj) formation

Ankur Saha, Monali Kawade, Hari P. Upadhyaya, Awadhesh Kumar, more

Chemical Physics > 2012 > 407 > Complete > 83-91

In one-color REMPI-TOF experiment, the photodissociation dynamics of POCl ₃ has been studied by photolyzing POCl ₃ and probing the chlorine atom photofragments, namely, Cl( ² P _3/2 ) and Cl ^∗ ( ² P _1/2 ) using 2+1 REMPI scheme, in the 234–236nm region. We have determined the centre-of-mass photofragment speed distribution, recoil anisotropy parameter,...

article

Dynamics of CCl bond fission in photodissociation of 2-furoyl chloride at 235nm

Ankur Saha, Hari P. Upadhyaya, Awadhesh Kumar, Prakash D. Naik, more

Chemical Physics > 2012 > 402 > Complete > 74-82

The photodissociation dynamics of 2-furoyl chloride at 235nm has been investigated, employing resonance-enhanced multiphoton ionization technique and time-of-flight mass spectrometry. Both the Cl fragments, Cl( ² P _J= _3/2 , relative quantum yield 0.85±0.11) and Cl ^∗ ( ² P _J _=1/2 ), have the recoil anisotropy parameter (β) value close to zero, and show...

article

The nascent OH detection in photodissociation of 2-(bromomethyl)hexafluoro-2-propanol at 193nm: Laser-induced fluorescence study

Yogesh N. Indulkar, Hari P. Upadhyaya, Awadhesh Kumar, Suresh B. Waghmode, more

Journal of Photochemistry & Photobiology, A: Chemistry > 2011 > 222 > 1 > 210-219

Photodissociation of 2-(bromomethyl)hexafluoro-2-propanol (BMHFP) and 3-bromo-1-propanol (BP), involving σC–Br*←nBr transition at 193nm, has been investigated by measuring laser-induced fluorescence spectra of the expected OH product. The OH channel is a minor dissociation pathway with a quantum yield of 0.17±0.05 in BMHFP, whereas it was not observed in BP. Partitioning of the available energy into...

article

Dynamics of Cl ( ² P _j ) Atom Formation in the Photodissociation of Fumaryl Chloride (ClCO − CH = CH − COCl) at 235 nm: A Resonance Enhanced Multiphoton Ionization (REMPI) Time-of-Flight (TOF) Study

Monali Kawade, Ankur Saha, Hari P. Upadhyaya, Awadhesh Kumar, more

The Journal of Physical Chemistry A > 2011 > 115 > 9 > 1538 - 1546

article

Dynamics of N−OH Bond Dissociation in Cyclopentanone and Cyclohexanone Oxime at 193 nm: Laser-Induced Fluorescence Detection of Nascent OH ( v ′′, J ′′)

Monali N. Kawade, Ankur Saha, Hari P. Upadhyaya, Awadhesh Kumar, more

The Journal of Physical Chemistry A > 2010 > 114 > 47 > 12369 - 12377

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PHOTODISSOCIATION DYNAMICS (8)
REMPI-TOF (5)
TRANSLATIONAL ENERGY RELEASE (5)
ANISOTROPY PARAMETER (4)
LASER INDUCED FLUORESCENCE (3)
1,2,5-THIDIAZOLE (2)
ENERGY PARTITIONING (2)
LAMBDA-DOUBLET RATIO (2)
SPIN–ORBIT RATIO (2)
(2+1) REMPI (1)
2-FUROYL CHLORIDE (1)
ABSORPTION CROSS-SECTION (1)
AL2O3 (1)
ATOMIC OXYGEN (1)
AUXIN MIMICS (1)
BROMO-PYRIDINES (1)
CARBOXYLIC ACIDS (1)
CHLORINE AND BROMINE ATOM FORMATION (1)
CHLORINE ATOM (1)
CN(B2Σ+) EMISSION SPECTRA (1)
COLLISION-INDUCED INTRAMOLECULAR ENERGY TRANSFER (1)
DENSITY FUNCTIONAL THEORY (DFT) (1)
DYNAMICS (1)
ELASTIC SCATTERING CROSS-SECTIONS (1)
ENOLIC-ACETONYLACETONE (1)
EROSION (1)
EXIT BARRIER (1)
FIRE EXTINGUISHER (1)
G4 METHOD (1)
HALOGENATED ALCOHOL (1)
HALOGENATED PYRIDINES (1)
HALOTHANE (1)
INERT GASES (1)
INTRAMOLECULAR HYDROGEN TRANSFER (1)
KETO–ENOL TAUTOMERISM (1)
KINETIC ENERGY RELEASE (1)
LASER PHOTOLYSIS (1)
LASER-INDUCED FLUORESCENCE (1)
METHOXYETHANOL (1)
MOLECULAR BEAM CHEMILUMINESCENCE (1)
NASCENT OH RADICAL DETECTION (1)
NASCENT STATE DISTRIBUTION (1)
NITRO COMPOUNDS (1)
OH FORMATION (1)
OH RADICAL REACTION (1)
OH SPECTROSCOPY (1)
OXIDATIVE DEGRADATION PATHWAYS (1)
PHOSPHOROUS OXYCHLORIDE (1)
POLYIMIDE (1)
POLYMERS (1)
QUANTUM YIELD (1)
QUARTZ CRYSTAL MICROBALANCE (1)
QUINCLORAC AND QUINMERAC (1)
QUINOLINE BASED HERBICIDES (1)
REACTION MECHANISM (1)
RECOIL ANISOTROPY PARAMETER (1)
REMPI (1)
SAMARIUM (1)
SPIN-ORBIT BRANCHING RATIO (1)
SPIN-ORBIT RATIO (1)
SPIN–ORBIT BRANCHING RATIO (1)
THIOPHENE (1)
THIOPHENE RING‐FRAGMENTATION (1)
UV PHOTOLYSIS (1)
UV–VIS ABSORPTION (1)
ÄTOMIC LAYER DEPOSITION (1)
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Search results for: Hari P. Upadhyaya

Theoretical Study on the Dissociation Mechanism of Thiophene in the UV Photoabsorption, Ionization, and Electron Attachment Processes

Theoretical studies on the kinetics and mechanism of hydroxyl radical reaction with quinclorac and quinmerac herbicides in aqueous media

Ground‐state dissociation pathways for the molecular cation of 2‐chlorothiophene: A time‐of‐flight mass spectrometry and computational study

Rate coefficients of hydroxyl radical reaction with dimethyl ether over a temperature range of 257–333 K

Kinetics of gas phase OH radical reaction with thiophene in the 272–353K temperature range: A laser induced fluorescence study

Resonance enhanced multiphoton ionization − time of flight (REMPI-TOF) detection of Br (2Pj) atoms in the photodissociation of 4-bromo-2,3,5,6-tetrafluoropyridine at 234nm: Effect of low-lying πσ* states

Dissociation pathways for the molecular cation of 3,4‐dichloro‐1,2,5‐thiadiazole: A time‐of‐flight mass spectrometry and computational study

Ground state dissociation pathways for 3,4,-dichloro-1,2,5-thiadiazole: Spectroscopic observation and fate of NCC(Cl2)NS isomer

Chlorine atom formation dynamics in the dissociation of halogenated pyridines after photoexcitation at 235nm: A resonance enhanced multiphoton ionization-time of flight (REMPI-TOF) study

Dynamics of Cl(2Pj) formation in the photodissociation of halogenated thiadiazole at 235nm: A resonance enhanced multiphoton ionization-time of flight (REMPI-TOF) study

Dynamics of OH formation in the photodissociation of enolic-acetonylacetone at 193nm

Photodissociation dynamics of 2-chloro-6-nitrotoluene and nitrocyclopentane in gas phase: Laser-induced fluorescence detection of OH

OH formation dynamics in 193nm photolysis of 2-methoxyethanol: A laser induced fluorescence study

Resonance enhanced multiphoton ionization time-of-flight (REMPI-TOF) study of tetrachloroethylene photodissociation at 235nm: Role of bound π-σC-Cl∗ state

Photoexcitation of 2-bromo-2-chloro-1,1,1-trifluoroethane (halothane) to repulsive surface nσ∗(C–Br) at 234 nm: Dynamics of C–Br and C–Cl bond rupture

Resonance enhanced multiphoton ionization time-of-flight (REMPI-TOF) study of phosphorous oxychloride (POCl3) dissociation at 235nm: Dynamics of Cl(2Pj) formation

Dynamics of CCl bond fission in photodissociation of 2-furoyl chloride at 235nm

The nascent OH detection in photodissociation of 2-(bromomethyl)hexafluoro-2-propanol at 193nm: Laser-induced fluorescence study

Dynamics of Cl ( ² P _j ) Atom Formation in the Photodissociation of Fumaryl Chloride (ClCO − CH = CH − COCl) at 235 nm: A Resonance Enhanced Multiphoton Ionization (REMPI) Time-of-Flight (TOF) Study

Dynamics of N−OH Bond Dissociation in Cyclopentanone and Cyclohexanone Oxime at 193 nm: Laser-Induced Fluorescence Detection of Nascent OH ( v ′′, J ′′)

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