Electronic spectroscopy of the Ã1A″← X̃1A′ system of CDF

Abstract

To further investigate the Renner-Teller (RT) effect and barriers to linearity and dissociation in the simplest singlet carbene, we recorded fluorescence excitation spectra of bands involving the pure bending levels 2(n)(0) with n = 0-9 and the combination states 1(1)(0)2(n)(0) with n = 1-8 and 2(n)(0)3(1)(0) with n = 0-5 in the A(1)A''<-- X(1)A' system of CDF, in addition to some weak hot bands. The spectra were measured under jet-cooled conditions using a pulsed discharge source, and rotationally analyzed to yield precise values for the band origins and rotational constants; fluorescence lifetimes were also measured to probe for lifetime lengthening effects due to the RT interaction. The derived A state parameters are compared with previous results for CHF and with predictions of ab initio electronic structure theory. The approach to linearity in the A state is evidenced in a sharp increase in the A rotational constant with bending excitation, and a minimum in the vibrational intervals near 2(9). A fit of the vibrational intervals for the pure bending levels yields an A state barrier to linearity in good agreement both with that previously derived for CHF and ab initio predictions. From the spectra and lifetime measurements, the onset of extensive RT perturbations is found to occur at a higher energy than in CHF, consistent with the smaller A constant.

Single vibronic level emission spectroscopy of the low-lying electronic states of NiI

“…NiI was produced using a pulsed discharge source, wherein Ni atoms sputtered from stainless steel electrodes (Type 303 stainless contains 8-10% Ni) reacted with an appropriate iodine-containing precursor seeded in $3 bar Ar (Airgas). Consistent with our previous study of CuOH using a similar source [20], a rotational temperature in the range of 50 K was determined from preliminary fits of 0009-2614/$ -see front matter Ó 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.cplett.2010.08.016 the fluorescence excitation spectra [21].…”

“…The unfocussed laser beam crossed the molecular beam 10 mm downstream, and the resulting fluorescence was collected by a two lens f/2.4 assembly and filtered via a combination of long-pass and short-pass cutoff filters (Corion or Edmund Scientific) prior to detection by a photomultiplier tube detector (Oriel) held at $À1000 V. Emission spectra were obtained using a 0.3 m spectrograph (Action SR303i with ISTAR CCD) in photon counting mode, typically with a 160 lm slit width and integration over 15,000 laser shots, and were calibrated using the output of an Fe:Ne hollow cathode lamp (Photron). Bands in the emission spectra were fit to a Gaussian line shape function, using Origin 7.5 software; previous studies have shown the validity of this approach [19][20][21]. The uncertainty in the derived band positions is ±2 cm À1 .…”

Electronic spectroscopy of the system of CDCl

“…The apparatus, pulsed discharge nozzle, and data acquisition procedures are identical to those used in previous studies of CHF, CDF, CHBr, CDBr, and CHCl [8,[44][45][46][47][48][49][50][51][52][53][54], and, therefore, only the important differences will be highlighted. The carbene CDCl was produced using a pulsed electrical discharge through a $1-2% mixture of CD 2 Cl 2 (Cambridge Isotope Labs, 99.9 atom % of D) seeded in high purity He.…”

“…Most recently, we reported comprehensive surveys of theà 1 A 00 X 1 A 0 system of CHBr, CDBr, and CHCl using fluorescence excitation and single vibronic level (SVL) emission spectroscopy [8,53,54]. In each case we recorded and analyzed many new cold bands, and reported the first measurement of theà 1 A 00 state C-H stretching frequencies following the observation of bands in the progressions 1 1 0 2 n 0 and 1 1 0 2 n 0 3 m 0 [36,46,52]. Exploiting these as pump transitions in SVL emission spectroscopy, we examined the vibrational level structure up to $9000 cm À1 above the vibronic origin ofX 1 A 0 , reporting many previously unobserved levels in both theX 1 A 0 and a 3 A 00 states and probing spin-orbit mixing in these systems in new detail.…”

“…Building upon the seminal work of Merer and Travis in the 1960's [9,10], and later work from the groups of Hirota [11][12][13][14][15][16][17][18], Sears [19][20][21][22][23][24][25][26][27][28][29][30][31][32][33], Kable [34][35][36], and Chang [37][38][39][40][41][42][43], our group has recently undertaken a systematic study of the monohalocarbenes CHF, CHCl, CHBr and their deuterated isotopomers, using a variety of methods including fluorescence excitation spectroscopy, lifetime measurements, polarization and Zeeman quantum beat spectroscopy, and single vibronic level emission spectroscopy [8,[44][45][46][47][48][49][50][51][52][53][54]. Most recently, we reported comprehensive surveys ...…”