The advent of ultrashort soft X-ray pulse sources permits the use of established gas-phase spectroscopy methods to investigate ultrafast photochemistry in isolated molecules with element and site specificity. In the present study, we simulate excited-state wavepacket dynamics of a prototypical process, the ultrafast photodissociation of methyl iodide. Using the simulation, we calculate time-dependent excited-state carbon edge photoelectron and Auger electron spectra. We observe distinct signatures in both types of spectra and show their direct connection to C–I bond dissociation and charge rearrangement processes in the molecule. We demonstrate at the CH3I molecule that the observed signatures allow us to map the time-dependent dynamics of ultrafast photoinduced bond breaking with unprecedented detail

Inhester, Ludger

Li, Zheng

Medvedev, Nikita

Wolf, Thomas

Zhu, Xiaolei

English

arXiv

Triplitt, Tom, \u2776

Furman University

Furman MagazineVolume 50Issue 4 Winter 2008 Article 481-1-2008Looking ahead: Summer offerings for all agesTom Triplitt '76Furman UniversityFollow this and additional works at: https://scholarexchange.furman.edu/furman-magazineThis Article is made available online by Journals, part of the Furman University Scholar Exchange (FUSE). It has been accepted for inclusion in FurmanMagazine by an authorized FUSE administrator. For terms of use, please refer to the FUSE Institutional Repository Guidelines. For more information,please contact scholarexchange@furman.edu.Recommended CitationTriplitt, Tom '76 (2008) "Looking ahead: Summer offerings for all ages," Furman Magazine: Vol. 50 : Iss. 4 , Article 48.Available at: https://scholarexchange.furman.edu/furman-magazine/vol50/iss4/48LOO K I N G  AHEAD: S U M M E R  OFFE R I N G S  FOR ALL AG ES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  . .  Although many might think that the pace a t  Furman eases d u ring the summer, the truth is that the campus barely has time to catch its breath between the end of school and the start of the "summer programs" season. From music and sports camps to special seminars and activities, the Office of Camps and Conferences br ings as many as 1 0,000 visitors to Furman each summer. This year, the Alumni  and Admissions offices are doing their part to keep the summer busy by offer­ing several programs that we bel ieve wi l l  be of interest to Furman graduates and/or their chi ldren. Quick synopses of these programs follow. > WHAT'S CALLING YOU NOW? The Li l ly Center for Theological Exploration of Vocation and the Alumni  Association are offering the second Li l ly Alumni  Retreat J u ly 24-27. The retreat's theme will once again be " What's Ca l l ing You Now? " This weekend event, for a lumn i  who graduated between 1 975 and 2000, is an invitation to revisit important dreams, explore the rea lities of adult life that get in the way of true cal l ing, and share with others life's wisdom accrued across several decades of experiences. James Mason '86, a school district admin istrator in Raymond, Miss. ,  attended the fi rst "What's Cal l ing You Now" retreat in  the summer of 2006. He writes that it provided him "the opportunity to step off the often relentless treadmi l l  of life and reconsider what really matters most. I found it amazing how the retreat helped to awaken some of my deepest passions about l ife, family and faith. 36 FURMAN I WINTER 2008 "Just as the Furman experience began a trans­formative journey within me over 25  years ago, the Li l ly retreat began another subtle yet seismic shift in how I wil l  view and pursue my vocational ca l l ing dur ing the second half of my l ife." We have l ined up several Furman professors who will offer their perspectives on the topic "Dreaming Dreams, Living Lives." You' l l  benefit from the tutelage of Charles Brewer, Wi l l iam R .  Kenan Professor of Psychology; J i m  Edwards, longtime professor of philosophy; Linda Bartlett, associate academic dean; and E l izabeth Smith, associate professor of political science. The staff of the Lil ly Center - Elaine Nocks, professor of psychology; David Bast, professor of Spanish; and Ann Quattlebaum, project coordinator - wi l l  lead other seminars and exploratory sessions. You' l l l ive in  Furman's North Village apartments and have plenty of free time to reflect on your expe­rience. Cost for the program is $250, plus $ 1 5 . 2 5  i f  you want the un iversity to supply bedding a n d  towels. For more information or to register, visit www.furman .edu/li l ly or call (864) 294-251 1 .  You can also go to www.furman.edu/fumag/index-fa l l06 .html and cl ick on the l ink to read an account of the 2006 retreat by Kevin Spears '92 .  > PLAN NING FOR COLLEGE The Admissions Office is developing a free " Planning for Col lege" seminar for a lumni  and prospective students on Friday, June 20 .  The program wi l l  include a primer on selecting a college and will feature tips for students and parents about various aspects of the college search, from what to look for dur ing campus visits to how to bui ld a list of potential colleges. It will also offer advice about preparing applications and helpful instruction on paying for college, including how to search for financial a id and scholarships. A panel  of Furman students wi l l  be on hand to offer their  perspectives about college life. For those who are considering applying to Furman, there wil l  be an opportunity to learn about the u n iversity's programs. More information is avai lable by e-mai l ing laura.simmons@furman.edu or by cal l ing the Alumni  Office (1 -800-PU RPLE3) or the Admissions Office, (864) 294-2034. > SUMMER SCHOLARS Alumni with rising jun iors or seniors in  high school, take note: Furman offers a Summer Scholars program of one-week enrichment classes for your students. The courses are taught by Furman faculty and staff and typically include a variety of learn ing experiences, ranging from lectures and smal l-group discussions to debates, laboratory work, field trips, group and individua l  projects, and other activities. This year's programs are scheduled July 1 5-21 and 22-28. Cost for the one-week courses is $800, which covers room, board, field tr ips and other fees. Students may participate for two weeks; those taking two classes receive a discount of $300. Summer Scholars l ive in  Lakeside (women's) Housing and have access to a l l  university facil ities. They also receive group and ind ividual counsel ing from Admissions representatives and students. This year's classes will include such topics as global information systems, ecology and environmen­ta l ism, languages (French and Span ish). leadership, acting, writing about fi lms and advertising design .  For  the fu l l  list, visit www.furman .edu/summerscholars. Deadl ine for applications is June 1 5 .  For additional i nformation, e-mail jean.adams@furman.edu or cal l  Jean at (864) 294-323 1 .  - TOM TRIPLITT '76 The author is director of the Alumni Association. 

Looking ahead: Summer offerings for all ages

Inhester, L.

Li, Z.

Zhu, X.

Medvedev, N.

Wolf, T.

MPG.PuRe

Supplementary InformationSpectroscopic Signature of Chemical BondDissociation Revealed by CalculatedCore-Electron SpectraLudger Inhester,∗,†,‖ Zheng Li,∗,‡,‖ Xiaolei Zhu,∗,¶ Nikita Medvedev,∗,§ andThomas J. A. Wolf∗,¶†Center for Free-Electron Laser Science, DESY, Notkestrasse 85, 22607 Hamburg, Germany‡Max Planck Institute for the Structure and Dynamics of Matter, D-22761 Hamburg, Germany¶Stanford PULSE Institute, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, MenloPark, CA 94025, USA§Institute of Physics and Institute of Plasma Physics, Academy of Science of Czech Republic, NaSlovance 1999/2, 18221 Prague 8, Czech Republic‖L.I. and Z.L. contributed equally to this work.E-mail: ludger.inhester@cfel.de; zheng.li@desy.de; zhuxl@stanford.edu;medvedev@ipp.cas.cz; tw2809@slac.stanford.eduIn this Supplementary Information, we present details of quantum dynamical model and acomparison of calculated data for CH3I and methane with available experimental data. We discussthe effect of finite time resolution on the observed signal. Further, we discuss the classical model ofcharge transfer between the core ionized carbon atom and the iodine atom,1,2 which is adapted toour case of CH3 and I with partial charges.S1Comparison of the calculated and experimental XPS binding en-ergiesDue to the lack of time-resolved experimental data for the photodissociation of CH3I, we can onlybenchmark the quality of our results by comparison of the C 1s binding energy in the electronicground state with experimental measurements. The experimental value of the binding energy is291.43 eV,3 which is in good agreement to our calculated value of 291.97 eV.Comparison of the calculated and experimental XPS and AESspectra of methane 0 0.002 0.004 0.006 0.008 0.01 0.012 0.014 0.016 0.018 0.02-10 -5  0  5  10  15  20  25  30Photoelectron cross section [arb. units]Relative binding energy [eV]calculated photoionization transitionsmeasured photoelectron countsFigure S1: Comparison of calculated and measured XPS. Experimental data extracted from Ref. 4.To verify our calculation procedure, we compare the XPS of methane with calculations employ-ing the same parameters (6-311G basis set, small active space comprising the lowest bound andthe nearest unbound orbitals) in Fig. S1. The measured data is extracted from Ref. 4. Accordingto this reference, the main photoelectron line is at 290.7 eV, which is in good agreement with ourS2calculated value of 291.2 eV. As can be seen in Fig. S1, the calculated data indicates a shake-upsatellite at 19.9 eV below the main line in good agreement with the experimental position of 18.9eV. The relative strength of shake-up to main line are also well reproduced in the calculation. 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 220  225  230  235  240  245  250  255  260Auger intensity [arb. units]Auger energy [eV]calculated Auger spectrummeasured Auger spectrumFigure S2: Comparison of calculated and measured AES. Experimental data extracted from Ref. 5.We further compare calculated AES for methane with available experimental data extractedfrom Ref. 5. For a better comparison, we convoluted the spectrum with Gaussians of 4eV full widthat half maximum and slightly shifted the calculated spectrum by 1.5 eV to lower energies. As canbe seen in Fig. S2, the resulting spectrum reproduces all the qualitative features of the experimentalAuger spectrum.XPS signature convolved with experimental time resolutionBased on our simulations in Fig. 2b of the main paper, we simulated the signatures which would beobservable in an experiment with finite time resolution. Usually, the time resolution of a optical/free-electron-laser experiments is determined by three components, the duration of the optical laserpulses, the duration of the x-ray pulses, and, either the shot-by-shot jitter of their relative timing orthe precision to which this jitter can be measured and corrected for. UV laser pulses with durationsS3Figure S3: Simulation of time-resolved XPS spectra assuming Gaussian UV and x-ray pulseswith a cross-correlation of 35 fs full width at half maximum (FWHM). a) Time-resolved XPS-spectrum assuming delta functions for the time profiles of pump and probe pulse. In comparisonto Fig. 2b in the main paper, the ground state XPS spectrum of CH3I is added for negative timedelays.b) Same spectrum as a), but with the ground state XPS spectrum subtracted. The groundstate contribution now appears as a negative contribution at positive time delays. c) Same spectrumas b), but convoluted with 35 fs FWHM Gaussian. d) Time-dependence at different positions of thedifference spectrum in c), 290 eV (blue), 292 eV (orange), and 295 eV (green).S4≤30 fs can be created without substantial effort. Many free electron lasers offer pulse durationsdown to ≤ 10 fs at appreciable intensities. The timing jitter between optical and x-ray pulses can bemeasured with 20 fs accuracy. In combination, this results in an achievable time resolution of 35fs. In Fig. S3a we are showing a time-dependent XPS spectrum assuming 100% excitation and adelta function temporal profile of UV and x-ray pulses. It shows the ground state spectrum of CH3Ifor negative time delays and the signatures of the bond dissociation from Fig.2b of the main paperat positive delays. Fig. S3b shows the result of subtracting the ground state XPS spectrum fromthe spectrum in Fig. S3a. This is a common representation of experimental data in time-resolvedx-ray spectroscopy. Here the relative intensities of spectral features are independent of the ratioof photoexcited molecules vs. molecules in the ground state. The ground state XPS spectrum nowappears as a negative signature for positive time delays. In Fig. S3c, the difference spectrum fromFig. S3b is convoluted with a Gaussian of 35 fs full width at half maximum in time, which accountsfor the achievable experimental time resolution discussed above. At realistic time resolutions, theshift of the strong excited state XPS feature starting at 290 eV to higher binding energies as wellas the shift of the weak satellite feature starting at 299.5 eV to lower binding energies are washedout. However, the switch in XPS cross-sections from the main excited state feature at early times tothe satellite feature at later times is still well observable. Fig. S3d shows lineouts from Fig. S3c.Time zero is clearly visible in the onset of the negative ground state bleach feature at 292 eV andthe initially intense positive feature at 290 eV binding energy. The switch in cross-section 20 fsafter UV excitation, marked by a vertical black line, is clearly visible in the decay of the 290 eVfeature and the delayed onset of the positive feature at 295 eV.Classical model of charge transferThe CH3 and I in the neutral CH3I molecule have partial charges −δq (CH3) and δq (I), whereδq = 0.15 is determined from the Mulliken charge analyses at Hartree-Fock level, since the cationafter screening-induced charge migration is correlated with the CH3 +I+ asymptote, we assume thatS5−50−40−30−20−100−3 −2 −1 0 1 2 3 4 5 6R=R0I CH3+Potential energy [eV]Internuclear distance [Å]Zic QΔeFigure S4: The illustration of potential and the charge (green sphere) to be transferred from iodineto the core ionized CH+3 . Zic = 1 is the charge of the ion core of I, and Q = 0.85 is the partialcharge of CH+3 . The dashed line represents the energy of the lowest bound electron in I atom, whichis to be transferred to CH+3 , which is Eb = −IP− |∆e|Q/R, and R = R0 = 2.136 Å, ∆e = −0.85.S6−50−40−30−20−100R=R0I CH3+−50−40−30−20−100R=RcPotential energy [eV]−50−40−30−20−100−2 0 2 4 6 8R>RcInternuclear distance [Å]Figure S5: The evolution of internuclear potential experienced by the charge to be transferred fromiodine to the core ionized CH+3 , for internuclear distance R to be the CH3I equilibrium distanceR0 = 2.136 Å, the critical distance Rc = 3.3 Å and R = 5.0 Å.S7fractional charge ∆e = −0.85 is transferred from I to CH3 , leaving behind an ion core I+ of chargeZic = 1. The partial charge of CH+3 before relaxation is Q = 1 − δq = 0.85, and the fractionalcharge is transferred in the potential shown in Fig. S4V (x) = −|∆e|Zic|x| −|∆eQ||R− x| , (S1)where R is the internuclear distance between C and I located at R and 0, and x is the coordinateof the moving charge modeled as point particle in the 1D system. The potential maximal in theinternuclear region 0 < x < R is found to be at x0 = R/[1 +√Q/Zic], andVm(x0) = −|∆e|[ZicR+2√ZicQR+QR]. (S2)Classically, the energy of the lowest bound electron isElbe = −IP− |∆e|QR, (S3)where IP = 10.45 eV is the 1st ionization energy of iodine atom, and the second term in Eq. S3is the perturbative energy from the CHQ+3 ion before charge migration. The charge migrationrequires naturally the condition Elbe ≥ Vm(x0) (see Fig. S5), it gives the expression of the criticalinternuclear distance RcR ≤ Rc = |∆e|[Zic + 2√ZicQIP], (S4)which is calculated to be Rc = 3.3 Å.References(1) Erk, B. et al. Imaging Charge Transfer in Iodomethane upon X-Ray Photoabsorption. Science2014, 345, 288–291.S8(2) Ryufuku, H.; Sasaki, K.; Watanabe, T. Oscillatory Behavior of Charge Transfer Cross Sectionsas a Function of the Charge of Projectiles in Low-Energy Collisions. Phys. Rev. A 1980, 21,745–750.(3) Bakke, A. A.; Chen, H.-W.; Jolly, W. L. A Table of Absolute Core-Electron Binding-Energiesfor Gaseous Atoms and Molecules. J. Electron. Spectrosc. Relat. Phenom. 1980, 20, 333–366.(4) Creber, D. K.; Tse, J. S.; Bancroft, G. M. Experimental and Theoretical Shakeup Studies. III.The 1s Shakeup in CH4, NH3, and H2O. J. Chem. Phys. 1980, 72, 4291–4299.(5) Kivimäki, A.; Neeb, M.; Kempgens, B.; Köppe, H. M.; Bradshaw, A. M. The C 1s Auger DecaySpectrum of the Molecule: The Effects of Vibrational Fine Structure, Double Excitations andShake-up Transitions. J. Phys. B: At. Mol. Opt. Phys. 1996, 29, 2701–2709.S9

Spectroscopic Signature of Chemical Bond Dissociation Revealed by Calculated Core-Electron Spectra

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Looking ahead: Summer offerings for all ages

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