We present a theoretical investigation of the impulsive orientation that can be induced by exposi... more We present a theoretical investigation of the impulsive orientation that can be induced by exposing a sample of state-selected NO molecules to the combination of a dc field and a short laser pulse. A strong degree of laserfield-free alignment and orientation is already achievable at moderate intensities and can be further improved by tailoring the temporal profile of the laser pulse. The alignment and orientation are only limited by the maximum value of the applied dc field and the pulse energy in the femtosecond laser pulse. Using an evolutionary algorithm coupled to a non-perturbative calculation of the timedependent Schrödinger equation, the solutions that are obtained suggest that cos θ = 0.964 is experimentally achievable.
Page 1. J. Phys. Chem. 1990, 94, 4839-4846 4839 Photofragment Imaging: The 266-nm Photolysis of C... more Page 1. J. Phys. Chem. 1990, 94, 4839-4846 4839 Photofragment Imaging: The 266-nm Photolysis of CD,I David W. Chandler,* Combustion Research Facility, Sandia National Laboratories, Livermore, California 94551 Maurice HM Janssen, ...
Relative integrated cross sections are measured for rotationally inelastic scattering of NO(2Pi(1... more Relative integrated cross sections are measured for rotationally inelastic scattering of NO(2Pi(1/2)),hexapole selected in the upper lambda-doublet level of the ground rotational state (j = 0.5), in collisions with He at a nominal energy of 514 cm(-1). Application of a static electric field E in the scattering region, directed parallel or antiparallel to the relative velocity vector v, allows the state-selected NO molecule to be oriented with either the N end or the O end towards the incoming He atom. Laser-induced fluorescence detection of the final state of the NO molecule is used to determine the experimental steric asymmetry, [formula: see text], which is equal to within a factor of (- 1) to the molecular steric effect, S(i-->f) is identical with (sigma(He-->NO) - (sigma(He-->ON))/(sigma(He-->NO) + sigma(He-->ON)). The dependence of the integral inelastic cross section on the incoming lambda-doublet component is also observed as a function of the final rotational ...
1 ingredient in experiments aimed at understanding and con-2 trolling molecular processes 1-6 . S... more 1 ingredient in experiments aimed at understanding and con-2 trolling molecular processes 1-6 . Samples of molecules that are 3 aligned or oriented even in the absence of external fields can 4 be obtained following the interaction with an intense laser 5 field 7-9 , enabling experiments in the molecular rather than 6 the laboratory frame 10-12 . However, the degree of molecular 7 orientation and alignment that can be achieved using a single 8 laser field is limited 13 and crucially depends on the initial states, 9 which are thermally populated. Here we report the successful 10 demonstration of a new technique for impulsive field-free ori-11 entation and alignment of molecules that combines an electro-12 static field, non-resonant femtosecond laser excitation 14 and 13 the preparation of state-selected molecules using a hexapole 2 .
We report a novel approach for determining the sign of permanent dipole moments, using nitric oxi... more We report a novel approach for determining the sign of permanent dipole moments, using nitric oxide [NOv 0] as an example. State-selected NO (j jmjj 1=2) molecules are focused using a hexapole and oriented in a strong dc electric field. The angular distributions of ionic fragments resulting from extreme ultraviolet single-photon and multiphoton dissociative ionization at 400 and 800 nm are measured and indicate that the dipole moment is negative (corresponding to N ÿ O ). The experiments thus rule out an error in the sign of the dipole of NO as the possible source of a remarkable discrepancy between previous theoretical and experimental work on orientation effects in bimolecular collisions involving oriented NO.
Relative integrated cross sections are measured for spin-orbit-conserving, rotationally inelastic... more Relative integrated cross sections are measured for spin-orbit-conserving, rotationally inelastic scattering of NO (2Pi1/2), hexapole-selected in the upper Lambda-doublet level of the ground rotational state (j = 0.5), in collisions with D2 at a nominal energy of 551 cm-1. The final state of the NO molecule is detected by laser-induced fluorescence (LIF). The state-selected NO molecule is oriented with either the N end or the O end toward the incoming D2 molecule by application of a static electric field E in the scattering region. This field is directed parallel or antiparallel to the relative velocity vector v. Comparison of signals taken for the different applied field directions gives the experimental steric asymmetry SA, defined by SA = (sigma v upward arrow downward arrow E - sigma v upward arrow upward arrow E)/(sigma v upward arrow downward arrow E + sigma v upward arrow upward arrow E), which is equal to within a factor of -1 to the molecular steric effect, Si-->f identical with (sigmaD2-->NO - sigmaD2-->ON)/(sigmaD2-->NO + sigmaD2-->ON). The dependence of the integral inelastic cross section on the incoming Lambda-doublet component is also measured as a function of the final rotational (jfinal) and Lambda-doublet (epsilonfinal) state. The measured steric asymmetries are similar to those previously observed for NO-He scattering. Spin-orbit manifold-conserving collisions exhibit a larger propensity for parity conservation than their NO-He counterparts. The results are interpreted in the context of the recently developed quasi-quantum treatment (QQT) of rotationally inelastic scattering [Gijsbertsen, A.; Linnartz, H.; Taatjes, C. A.; Stolte, S. J. Am. Chem. Soc. 2006, 128, 8777]. The QQT predictions can be inverted to obtain a fitted hard-shell potential that reproduces the experimental steric asymmetry; this fitted potential gives an empirical estimate of the anisotropy of the repulsive interaction between NO and D2. QQT computation of the differential cross section using this simple model potential shows reasonable agreement with the measured differential cross sections.
Chemical reaction dynamics: Combination of two models. [The Journal of Chemical Physics 93, 4874 ... more Chemical reaction dynamics: Combination of two models. [The Journal of Chemical Physics 93, 4874 (1990)]. Glenn T. Evans, Eddy van Kleef, Steven Stolte. Abstract. The methods of classical kinetic theory for rigid nonspherical ...
The CF3I(5pπ–6s) Rydberg transitions in the energy range 56 700–64 000 cm−1 are investigated usin... more The CF3I(5pπ–6s) Rydberg transitions in the energy range 56 700–64 000 cm−1 are investigated using (2+1) resonance-enhanced multiphoton ionization. The polarization of the two-photon transitions is used to definitely assign the symmetries of the resonant intermediate states. The four allowed electronic transitions in the (5pπ–6s) manifold have been assigned and some vibrational constants in the excited states have been determined. Hot band spectra have been obtained in a supersonic expansion of CF3I through an oven. The upper spin–orbit components (the 2E1/2 ion core states) are perturbed by a dissociative state at approximately 63 000 cm−1, possibly the σ–σ* transition centered on the C–I bond. Density functional calculations have been performed in order to help determine the nature of the perturbing states. Vibronic interactions in the excited states are investigated, and evidence is seen for quadratic Jahn–Teller interactions for ν6 in the lower (2E3/2) spin–orbit state.
CO molecules in a supersonic molecular beam are resonantly excited from the X 'Z+, u"=O ground st... more CO molecules in a supersonic molecular beam are resonantly excited from the X 'Z+, u"=O ground state to the a 'lI, u'=O metastable state using pulsed laser radiation at 206 nm. In the excitation region a static electric field is applied to split individual M components of a given rotational line of this electronic transition. The splitting can be made larger than the Fourier-limited bandwidth of the pulsed radiation source and specific M levels in the a 'lI state can be populated. Peak fluxes of IO" ( 10") oriented CO a%,, u'=O, J'= 1, M'= 1 (a 'fl,, u'=O, J'=2, M'=2) molecules per second are obtained.
Electronic energy transfer in the E(0g+) D(0+) system of I2 is investigated in an experiment, whe... more Electronic energy transfer in the E(0g+) D(0+) system of I2 is investigated in an experiment, where single rovibrational quantum states are prepared, single collision conditions prevail, and the final states have been determined from dispersed fluorescence. In I (E) X (X Ar, N2, 02) the collisional decay is found to be governed by minimum energy transfer. With (X I2) an anomalous behaviour is found for the initially prepared E, v 8, J 56 level, which is tentatively ascribed to vibrational excitation of the collision partner.
We present a theoretical investigation of the impulsive orientation that can be induced by exposi... more We present a theoretical investigation of the impulsive orientation that can be induced by exposing a sample of state-selected NO molecules to the combination of a dc field and a short laser pulse. A strong degree of laserfield-free alignment and orientation is already achievable at moderate intensities and can be further improved by tailoring the temporal profile of the laser pulse. The alignment and orientation are only limited by the maximum value of the applied dc field and the pulse energy in the femtosecond laser pulse. Using an evolutionary algorithm coupled to a non-perturbative calculation of the timedependent Schrödinger equation, the solutions that are obtained suggest that cos θ = 0.964 is experimentally achievable.
Page 1. J. Phys. Chem. 1990, 94, 4839-4846 4839 Photofragment Imaging: The 266-nm Photolysis of C... more Page 1. J. Phys. Chem. 1990, 94, 4839-4846 4839 Photofragment Imaging: The 266-nm Photolysis of CD,I David W. Chandler,* Combustion Research Facility, Sandia National Laboratories, Livermore, California 94551 Maurice HM Janssen, ...
Relative integrated cross sections are measured for rotationally inelastic scattering of NO(2Pi(1... more Relative integrated cross sections are measured for rotationally inelastic scattering of NO(2Pi(1/2)),hexapole selected in the upper lambda-doublet level of the ground rotational state (j = 0.5), in collisions with He at a nominal energy of 514 cm(-1). Application of a static electric field E in the scattering region, directed parallel or antiparallel to the relative velocity vector v, allows the state-selected NO molecule to be oriented with either the N end or the O end towards the incoming He atom. Laser-induced fluorescence detection of the final state of the NO molecule is used to determine the experimental steric asymmetry, [formula: see text], which is equal to within a factor of (- 1) to the molecular steric effect, S(i-->f) is identical with (sigma(He-->NO) - (sigma(He-->ON))/(sigma(He-->NO) + sigma(He-->ON)). The dependence of the integral inelastic cross section on the incoming lambda-doublet component is also observed as a function of the final rotational ...
1 ingredient in experiments aimed at understanding and con-2 trolling molecular processes 1-6 . S... more 1 ingredient in experiments aimed at understanding and con-2 trolling molecular processes 1-6 . Samples of molecules that are 3 aligned or oriented even in the absence of external fields can 4 be obtained following the interaction with an intense laser 5 field 7-9 , enabling experiments in the molecular rather than 6 the laboratory frame 10-12 . However, the degree of molecular 7 orientation and alignment that can be achieved using a single 8 laser field is limited 13 and crucially depends on the initial states, 9 which are thermally populated. Here we report the successful 10 demonstration of a new technique for impulsive field-free ori-11 entation and alignment of molecules that combines an electro-12 static field, non-resonant femtosecond laser excitation 14 and 13 the preparation of state-selected molecules using a hexapole 2 .
We report a novel approach for determining the sign of permanent dipole moments, using nitric oxi... more We report a novel approach for determining the sign of permanent dipole moments, using nitric oxide [NOv 0] as an example. State-selected NO (j jmjj 1=2) molecules are focused using a hexapole and oriented in a strong dc electric field. The angular distributions of ionic fragments resulting from extreme ultraviolet single-photon and multiphoton dissociative ionization at 400 and 800 nm are measured and indicate that the dipole moment is negative (corresponding to N ÿ O ). The experiments thus rule out an error in the sign of the dipole of NO as the possible source of a remarkable discrepancy between previous theoretical and experimental work on orientation effects in bimolecular collisions involving oriented NO.
Relative integrated cross sections are measured for spin-orbit-conserving, rotationally inelastic... more Relative integrated cross sections are measured for spin-orbit-conserving, rotationally inelastic scattering of NO (2Pi1/2), hexapole-selected in the upper Lambda-doublet level of the ground rotational state (j = 0.5), in collisions with D2 at a nominal energy of 551 cm-1. The final state of the NO molecule is detected by laser-induced fluorescence (LIF). The state-selected NO molecule is oriented with either the N end or the O end toward the incoming D2 molecule by application of a static electric field E in the scattering region. This field is directed parallel or antiparallel to the relative velocity vector v. Comparison of signals taken for the different applied field directions gives the experimental steric asymmetry SA, defined by SA = (sigma v upward arrow downward arrow E - sigma v upward arrow upward arrow E)/(sigma v upward arrow downward arrow E + sigma v upward arrow upward arrow E), which is equal to within a factor of -1 to the molecular steric effect, Si-->f identical with (sigmaD2-->NO - sigmaD2-->ON)/(sigmaD2-->NO + sigmaD2-->ON). The dependence of the integral inelastic cross section on the incoming Lambda-doublet component is also measured as a function of the final rotational (jfinal) and Lambda-doublet (epsilonfinal) state. The measured steric asymmetries are similar to those previously observed for NO-He scattering. Spin-orbit manifold-conserving collisions exhibit a larger propensity for parity conservation than their NO-He counterparts. The results are interpreted in the context of the recently developed quasi-quantum treatment (QQT) of rotationally inelastic scattering [Gijsbertsen, A.; Linnartz, H.; Taatjes, C. A.; Stolte, S. J. Am. Chem. Soc. 2006, 128, 8777]. The QQT predictions can be inverted to obtain a fitted hard-shell potential that reproduces the experimental steric asymmetry; this fitted potential gives an empirical estimate of the anisotropy of the repulsive interaction between NO and D2. QQT computation of the differential cross section using this simple model potential shows reasonable agreement with the measured differential cross sections.
Chemical reaction dynamics: Combination of two models. [The Journal of Chemical Physics 93, 4874 ... more Chemical reaction dynamics: Combination of two models. [The Journal of Chemical Physics 93, 4874 (1990)]. Glenn T. Evans, Eddy van Kleef, Steven Stolte. Abstract. The methods of classical kinetic theory for rigid nonspherical ...
The CF3I(5pπ–6s) Rydberg transitions in the energy range 56 700–64 000 cm−1 are investigated usin... more The CF3I(5pπ–6s) Rydberg transitions in the energy range 56 700–64 000 cm−1 are investigated using (2+1) resonance-enhanced multiphoton ionization. The polarization of the two-photon transitions is used to definitely assign the symmetries of the resonant intermediate states. The four allowed electronic transitions in the (5pπ–6s) manifold have been assigned and some vibrational constants in the excited states have been determined. Hot band spectra have been obtained in a supersonic expansion of CF3I through an oven. The upper spin–orbit components (the 2E1/2 ion core states) are perturbed by a dissociative state at approximately 63 000 cm−1, possibly the σ–σ* transition centered on the C–I bond. Density functional calculations have been performed in order to help determine the nature of the perturbing states. Vibronic interactions in the excited states are investigated, and evidence is seen for quadratic Jahn–Teller interactions for ν6 in the lower (2E3/2) spin–orbit state.
CO molecules in a supersonic molecular beam are resonantly excited from the X 'Z+, u"=O ground st... more CO molecules in a supersonic molecular beam are resonantly excited from the X 'Z+, u"=O ground state to the a 'lI, u'=O metastable state using pulsed laser radiation at 206 nm. In the excitation region a static electric field is applied to split individual M components of a given rotational line of this electronic transition. The splitting can be made larger than the Fourier-limited bandwidth of the pulsed radiation source and specific M levels in the a 'lI state can be populated. Peak fluxes of IO" ( 10") oriented CO a%,, u'=O, J'= 1, M'= 1 (a 'fl,, u'=O, J'=2, M'=2) molecules per second are obtained.
Electronic energy transfer in the E(0g+) D(0+) system of I2 is investigated in an experiment, whe... more Electronic energy transfer in the E(0g+) D(0+) system of I2 is investigated in an experiment, where single rovibrational quantum states are prepared, single collision conditions prevail, and the final states have been determined from dispersed fluorescence. In I (E) X (X Ar, N2, 02) the collisional decay is found to be governed by minimum energy transfer. With (X I2) an anomalous behaviour is found for the initially prepared E, v 8, J 56 level, which is tentatively ascribed to vibrational excitation of the collision partner.
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