Time-resolved double resonance signal showing depopulation of the (0,1,1,20,00), J = 0 level as a function of IR-UV pulse time delay. This trace was recorded with 200 mTorr of C2H2 at room temperature. The smooth line is a single exponential fit to the experimental data.
IR-UV double resonance spectrum of the (0,1,1,20,00) overtone transition. This trace was recorded with the UV probe laser set to monitor the population of (0,1,1,20,00), J = 0. The C2H2 pressure was 52 mTorr and the IR-UV pulse delay time was 200 ns.
UV-scanned double resonance spectra following IR excitation of (1,0,1,00,00) J i = 8. Data were recorded using a C2H2 pressure of 100 mTorr. (a) With a pump-probe delay of 20 ns the spectrum is dominated by the rotational lines that originate from J = 8. The baseline signal level is determined by the scattered laser light. (b) At a pump-probe delay time of 200 ns the spectrum shows resolved spectral lines from levels populated by energy transfer and a shift in the baseline caused by the CIQCB.
Time-resolved double resonance signals for energy transfer following excitation of the (1,0,1,00,00) state. The probe laser was set to monitor the J f = 2 level. These traces are for initial excitation of (a) J i = 0, (b) J i = 4, (c) J i = 6 and (d) J i = 8. The smooth curves illustrate decomposition of the signals into components from the monitored rotational state and the collision-induced background. These measurements were carried out at a C2H2 pressure of 100 mTorr.
Partial energy level diagram for the ortho levels of the [2,10,0] polyad. See text for details.
Double resonance spectra showing VET between (1,0,1,00,00) and the (0,2,0,31,1−1), (0,1,1,20,00), and (1,1,0,11,1−1) states. The top spectrum was recorded with the UV laser set to detect (1,1,0,11,1−1) J f = 6 for 55 mTorr C2H2 and a 220 ns delay. The middle trace was recorded with detection of (0,1,1,20,00) J f = 6 for 51 mTorr C2H2 and a 220 ns delay. The bottom trace is for detection of (0,2,0,31,1−1) J f = 2 for 55 mTorr C2H2 and a 120 ns delay.
UV-scanned double resonance spectrum following IR excitation of (1,0,1,00,00) J i = 8. Data were recorded using a C2H2 pressure of 50 mTorr and a pump-probe delay time of 800 ns. The rotational lines originate from the (1,1,0,20,00)/(0,0,2,00,00) dyad pair. Traces (a) and (b) are the observed spectrum and a simulation generated using the program PGOPHER.54 See text for details.
IR-scanned double resonance spectrum obtained by monitoring the J f = 5 level of the lower-energy dyad of (1,1,0,20,00)/(0,0,2,00,00) (state |I〉). Trace recorded at a C2H2 pressure of 51 mTorr with a pump-probe delay time of 70 ns.
State-to-state RET rate constants plotted against the energy difference between the initial and final states for endothermic transfer within the (0,1,1,20,00) state. Nonlinear least-square fits to Eqs. (6)–(8) are shown. The dashed, dotted, and solid lines are for the EGL, PGL, and PEGL models, respectively.
Observed and simulated spectra for RET within the (0,1,1,20,00) manifold. The upper trace is a double resonance spectrum recorded for J f = 6 with a C2H2 pressure of 50 mTorr and a pump-probe delay time of 200 ns. The lower trace is a master equation simulation that used the rate constant matrix generated from the PEGL model.
Total removal rate constants for selected rotational levels of C2H2 (0,1,1,20,00).
State-to-state RET rate constants (k i,f ) for C2H2 (0,1,1,20,00).
Total removal rate constants for selected rotational levels of C2H2 (1,0,1,00,00).
State-to-state RET rate constants (k i,f ) for C2H2 (1,0,1,00,00).
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