Inorganic ChemistryThe mass spectrum of (C2H5Si)4Se6 was obtained by direct injection of a sample into an inlet system heated at just below 200°. Since the maximum observable m/e with our spectrometer is at about 675, the largest fragments observed were due to (CgHsjsSiiSes, the parent less an ethyl group. The most intense peaks were in the region of m/e 474-495, corresponding to (C2H5Si)3Se4.(CH3Sn)2S3.-Methyltrichlorostannane (4.4 g, 1.8 mmoles) was dissolved in 30 ml of acetone.A solution of 6.7 g (2.8 mmoles) of sodium sulfide enneahydrate in 12 ml of water was added dropwise, resulting in an exothermic reaction. After 0.5 hr, 50 ml of water was added, precipitating a white solid (1.6 g). After extraction with water for 2 hr to remove sodium sulfide, the water-insoluble product was vacuum dried over phosphoric anhydride for 4 days.
The laser-excited vibrational fluorescence method has been used to obtain room temperature (294±2°K) vibrational relaxation rates for pure HF and in HF-additive mixtures. Measurement of the quenching of HF(v=1) fluorescence in HF–HF and HF-additive collisions has yielded the following total deactivation rates: HF†Ar<60 sec−1· torr−1, HF†N2=(1.25 ± 0.6) × 102 sec−1· torr−1, HF†D2=(3.7± 0.4)× 103sec−1· torr−1, HF†H2=(2.4 ± 0.3) × 104sec−1· torr−1, HF†CO2=(5.9± 0.2)× 104 sec−1· torr−1, and HF†H2O≈ HF†D2O=(4.1± 0.5)× 106 sec−1· torr−1. The self-relaxation rate for HF was found to be HF†HF=(8.74± 0.1)× 104 sec−1 torr−1 in dilute Ar mixtures and also with other additives. A slower rate (4.4± 0.3)× 104 sec−1· torr−1 has been measured in pure HF and is believed to indicate nonequilibrium of the rotational degrees of freedom during self-relaxation of HF. Observation of 4.3 μ fluorescence from CO2(00°1) and double exponential fluorescent decay from HF–H2 mixtures has led to the following rates for CO2(00°1) and H2(v=1) deactivation: CO2†HF=(5.3± 0.2)× 104 sec−1torr−1, and H2†HF=(6.3± 0.4)× 104 sec−1torr−1. The room temperature data are much faster than predicted from an extrapolation of the available high-temperature shock tube results. The equal, near gas kinetic rates found for HF relaxation by H2O and D2O suggest that strong chemical bonding forces may be responsible for the HF-water relaxation.
Vibrational energy transfer rates in CO2–CO mixtures have been measured from 163 to 406 °K using the laser excited vibrational fluorescence method. The near resonant V→V transfer step CO(v=1)+CO2(000)ke⇌ke′ CO(v=0)+CO2(001)+ΔE=−206 cm−1 has been measured in the endothermic direction and after detailed balancing [ke′=ke exp(−ΔE/kT)] is in excellent agreement with data taken in the exothermic direction at and above room temperature. V→R,T quenching of the CO2(001) level by CO2 and CO has also been studied. The CO2 self-relaxation rate reverses in temperature dependence between 250–300 °K with rates becoming progressively faster as temperature decreases. The total quenching rate for CO2 deactivation in CO2–CO collisions behaves similarly to the self-relaxation rate. It was not possible in the present analysis to separate and distinguish the pathways for V→R,T deactivation in equilibrated CO2–CO mixtures. The cross relaxation terms (CO+2–CO) and (CO+–CO 2) are both expected to be important at low temperatures.
Laser-induced fluorescence studies of CO collisional relaxation have been carried out using the output of a frequency-doubled, pulsed CO2 laser as a direct source of CO(ν = 1) excitation. Energy transfer cross sections at 298 °K are reported for CO in collisions with He, Ar, H2, D2, N2, O2, Cl2, NO, CH4, CF4, and SF6. The D2–D2 self-relaxation rate was also obtained from the analysis of CO–D2 mixtures.
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