Presentation on theme: "1 DETERMINATION OF DIFFERENTIAL CROSS SECTIONS OF THE STATE-TO-STATE INELASTIC COLLISIONS IN BULBS. A THREE-DIMENSIONAL SLICED FLUORESCENCE IMAGING STUDY."— Presentation transcript:
1 DETERMINATION OF DIFFERENTIAL CROSS SECTIONS OF THE STATE-TO-STATE INELASTIC COLLISIONS IN BULBS. A THREE-DIMENSIONAL SLICED FLUORESCENCE IMAGING STUDY Kuo-mei Chen Department of Chemistry The 68 th OSU International Symposium on Molecular Spectroscopy June 20, 2013 National Sun Yat-sen University, Kaohsiung, Taiwan, ROC
2 CHEMICAL REACTION KINETICS AND DYNAMICS SPECTROSCOPY IDENTIFICATION OF CHEMICAL SPECIES AND INTERNAL STATES TO THE ELECTRONIC, VIBRATIONAL, ROTATIONAL, AND FINE STRUCTURE (SPIN-ORBIT, -DOUBLET, HYPER-FINE) RESOLVING POWER IMAGING INFORMATION ON VELOCITY DISTRIBUTIONS, ANGULAR DISTRIBUTIONS, AND ANGLE-RESOLVED ANGULAR MOMENTUM POLARIZATIONS
3 SPECTROSCOPY AND IMAGING METHODS IN CHEMICAL DYNAMICS ION IMAGING REMPI DETECTION SCHEME AND MOLECULAR BEAM ENVIRONMENTS SLICED FLUORESCENCE IMAGING LIF DETECTION SCHEME AND BULB ENVIRONMENTS (BEAM CONDITION OPTIONAL)
4 Can we execute dynamic studies in bulbs? Can we execute state-to-state dynamic studies in bulbs? Their answers could be provided by * a) sliced fluorescence imaging, and b) 3D sliced fluorescence imaging + optical-optical double resonance spectroscopy. * Chen, Yang and Chen, Phys. Chem. Chem. Phys., 11, 7111 (2009). Chen and Chen, J. Chem. Phys., 133, (2010) Chen and Chen, Phys. Chem. Chem. Phys., 13, 5610 (2011).
5 Photo-induced dynamic processes can be studied in a bulb environment by the sliced fluorescence imaging method.
6 REDUCTION OF IMAGE BLURRING The combination of sliced crescents (red) is equivalent to a 2D projection of the fluorescent Newton sphere from a single photolysis center at the origin.
7 EXPERIMENTAL APPARATUS
8 ICN 266 nm I * + CN I + CN PHOTODISSOCIATION OF ICN
9 EXPERIMENTAL RESULTS OF SFL STUDIES ON CN
10 THREE-DIMENSIONAL SLICED FLUORESCENCE IMAGING (3DSFI) This novel experimental method aims at dynamic studies of molecular photodissociation processes, and photo-initiated inelastic and reactive collisions in a bulb environment. 3DSFI combines the sliced fluorescence imaging techniques and a double resonance spectroscopic detection scheme to acquire the central slice of state-selected Newton spheres of scattering products.
14 A X excitation spectrum of CN photofragments (266 nm photolysis of ICN)
15 FLUORESCENCE INTENSITY (A.U) PROBE LASER WAVEUMBER (cm -1 ) Q 1 (7) and P 21 (7) R 21 (7) OODR (B A X) excitation spectrum of CN photofragments (266 nm photolysis of ICN) Intermediate state: J = 7.5, F 1, f state was prepared by Q 1 (7) transition of the A X (3,0) band. ICN: 3 mTorr Delay time: 10 ns (photolysis-probe I) 300 ns (probe I-probe II)
16 3DSFI EXPERIMENT OF CN PHOTOFRAGMENTS
17 SUMMARY ON 3DSFI 3D SLICED FLUORESCENCE IMAGING (BASED ON DOUBLE RESONANCE SPECTROSCOPY) SIMPLICITY VERSATILITY (OODRS, IODRS) BULB ENVIRONMENT (RELEVANT TO THE MORE FAMILIAR WORKING CONDITIONS OF CHEMISTS) STATE-TO-STATE DYNAMIC STUDIES PHOTO-INITIATED CHEMICAL REACTIONS DYNAMICAL INFORMATION CAN BE EXTRACTED FROM THE EXPERIMENTAL IMAGES BY UTILIZING THE NEWLY DEVELOPED FRAMEWORKS
19 OODR (B A X) excitation spectrum of CN photofragments (266 nm photolysis of ICN) Intermediate state: J = 7.5, F 1, f state was prepared by Q 1 (7) transition of the A X (3,0) band. ICN: 3 mTorr ; He: 8 mTorr Delay time: 10 ns (photolysis-probe I) 800 ns (probe I-probe II)
20 3D SLICED FLUORESCENCE IMAGING OF STATE-TO- STATE INELASTIC COLLISIONS pumpedcollision-populated Pumped state: J = 7.5, F 1, f state was prepared by Q 1 (7) transition of the A X (3,0) band. Probe transitions: Q 1 (7) of the B A (3,3) band (pumped state) Q 1 (5) of the B A (3,3) band (collision-populated state, ) ICN: 3 mTorr Collider: He at 8 mTorr ~3.7 mm
21 DETERMINATION OF STATE-TO-STATE DIFFERENTIAL CROSS SECTIONS OF INELASTIC COLLISIONS IN A PHOTOLOC EXPERIMENT The central slice of the Newton sphere of collision-populated AB( J 3 ;v, ) is probed by the 3D sliced fluorescence imaging. state generation: state selection: state-to-state collision:
22 All the detectable reaction events in a 3DSFI experiment occur in the origin. No “fly-in” or “fly-out” problem with respect to the detection plane. No density-to-flux transformation in image intensity calibration.
23 FRAMEWORK OF PHOTOLOC EXPERIMENTS * Angular-velocity distributions of the center-of-mass Integrating over, , and , one gets Angular-velocity distributions of the product AB in the center-of-mass frame * Shafer, Orr-Ewing, Simpson, Xu, and Zare, CPL 212, 155 (1993). DCS
24 Integrating over, one gets From the result of Schulten and Gordon *, we can prove that the velocity distribution of product AB in the laboratory frame after integrating over is given by The experimental image I(r, ) is given by where r = vt, a = u c t, b = ut, and t is the delay time. * Schulten and Gordon, JCP 64, 2918 (1976).
25 DOUBLE LEGENDRE MOMENT ANALYSES IN THE DETERMINATION OF DCS (a) (b) (c) F(r, ; a, b) CENTRAL SLICED EXPERIMENTAL IMAGE 2D zeroth-order Legendre moment 1D m-th-order Legendre moment numerical values of a m coefficients DCS r R2R2 R1R1 r n G(r; R 1,R 2 ) anan 1
26 SUMMARY ON DETERMINATION OF DCS AND KINETIC ENERGY RELEASE OF CO-PRODUCTS a. The intensity distribution of the central sliced image, along with its outer and inner ring sizes, provide all the clues to decipher the DCS and the kinetic energy release of co-products. b. A double Legendre moment analysis framework has been established. c. The framework is applicable to a fixed or a continuously distributed recoil speeds in the center-of-mass reference frame. d. The combination of the PHOTOLOC methodology and the 3DSFI method is very powerful to study dynamic processes in bulbs.
27 f F 1 e F e F 1 + f F 2 e F 1 f F 2 Q 1 (7) + P 21 (7) Q 1 (5) +P 21 (5) f + e Q 1 (7) J 7 6 J N 7 J J N N 5 (b) (a) f e + f e 7 6 N 5 e F 1 f F 2 3D SLICED FLUORESCENCE IMAGING OF STATE-TO-STATE INELASTIC COLLISIONS ICN: 3 mTorr Collider: He at 8 mTorr
29 YES, WE CAN EXECUTE DYNAMIC STUDIES IN BULBS. * Financial supports from NSC, Taiwan and National Sun Yat-sen University, Kaohsiung are greatly acknowledged. † Research co-workers: Dr. Yu-wei Chen, Mr. Tsung-hang Yang, and Mr. Feng-chu Wang.